Monday

July 25, 2016
Number of results: 84,112

**physics**

a girl of mass 40 kg is skating at a constant speed of 1 m/s. supposed she doubles her speed, what will be the change in her kinetic energy?
*January 25, 2011 by Anonymous*

**physics**

a girl of mass 40 kg is skating at a constant speed of 1 m/s. supposed she doubles her speed, how much work will be needed to double her speed?
*January 7, 2013 by merlyn*

**physics**

A skier of mass 70kg is pulled up a slope by a motor-driven cable. The acceleration of gravity is 9.8m/s^2. How much work is required to pull him 60m up a 30.7º slope (frictionless) at a constant speed of 3 m/s? answer in units of kJ. In this question, I think I gotta use mgh ...
*September 17, 2006 by puff puff*

**Physical Science**

Can someone please check these answers for me? Write T for True or F for False for each statement: 1.Kinetic energy is the energy of motion - T 2.Kinetic energy doesn't depend on an object's direction. - T 3.When an object stops moving, its kinetic energy is zero. - T 4.As the...
*April 20, 2009 by mysterychicken*

**physics**

A boulder flies through the air at 14.5 m/s with kinetic energy 310 J. What's its mass? What's the boulder's kinetic energy if its speed doubles? What's the boulder's kinetic energy if its speed is halved?
*February 9, 2016 by leon*

**Physics**

A 70.0-kg runner has a speed of 5.90 m/s at one instant during a long-distance event.What is the runner's kinetic energy at this instant? If he doubles his speed to reach the finish line, by what factor does his kinetic energy change?
*September 27, 2011 by Anonymous*

**physics**

A 65.0-kg runner has a speed of 5.20 m/s at one instant during a long-distance event. (a) what is the runner's kinetic energy at this instant? (b) if he doubles his speed to reach the finish line, by what factor does his kinetic energy change
*March 1, 2012 by corey*

**physics**

A 59.0-kg runner has a speed of 3.20 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant? KEi = J (b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi =
*February 23, 2012 by Darcie*

**physics**

A 56.0-kg runner has a speed of 3.10 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant? KEi = J (b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi
*February 27, 2016 by sherry*

**physics**

A 61.0-kg runner has a speed of 3.20 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant? KEi = J (b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? KEf KEi =
*February 29, 2016 by sara*

**physics**

A 57.5-kg runner has a speed of 5.80 m/s at one instant during a long-distance event. (a) What is the runner's kinetic energy at this instant? 967.15 J (b) If he doubles his speed to reach the finish line, by what factor does his kinetic energy change? im having trouble with ...
*October 5, 2015 by zach*

**physics**

A car has a flywheel ( a diks of R=0.2m and uniformly distributed mass M=100kg) that can convert 25% of the rotational kinetic energy into translational kinetic energy. The mass of the car is 1000kg ( including flywheel). Suppose the car is at rest, and the flywheel has a ...
*December 30, 2013 by Al*

**Physics**

A 3.2 kg block with a speed of 11 m/s collides with a 11 kg block that has a speed of 3.3 m/s in the same direction. After the collision, the 3.2 kg block is observed to be traveling in the original direction with a speed of 6.4 m/s. (a) What is the velocity of the 11 kg block...
*November 1, 2011 by Ashley*

**physics kinetic energy**

a) if a particle's speed decreases by a factor of four, by what factor does its kinetic energy change? b) particle A has three times the mass and twice the kinetic energy of particle B. What is the speed ratio VA / VB?
*October 31, 2008 by joyce*

**8th grade physical science**

You are on roller blades on top of a small hill. Your PE is 1,000.0 Joules. The last time you check your mass was 60.0 kg. What is the height of the hill? if you start skating down this hill, your poetntial energy will be converted to kinetic. At the bottom of the hill, the ...
*January 19, 2012 by Misty*

**Algebra II**

The kinetic energy of a moving body is directly proportional to its mass and the square of its speed. If the mass of a bullet is halved, by what factor must its speed be increased to have the same kinetic energy as before?
*November 21, 2011 by Arielle*

**Algebra II**

The kinetic energy of a moving body is directly proportional to its mass and the square of its speed. If the mass of a bullet is halved, by what factor must its speed be increased to have the same kinetic energy as before?
*November 21, 2011 by Joe*

**Algebra II**

The kinetic energy of a moving body is directly proportional to its mass and the square of its speed. If the mass of a bullet is halved, by what factor must its speed be increased to have the same kinetic energy as before?
*November 22, 2011 by Ashley*

**Math **

the kinetic energy of moving body ids directly praportional to its mass and the square of its speed.if the mass of a bullet is halved by what factor must its speed be increased to have the same kinetic energy as before?
*November 21, 2011 by rahul patel*

**science**

a girl on a motorbike passes by at a speed of 15 m/sec.her mass is 40 kg. what is the kinetic energy
*September 19, 2010 by sergio*

**Physics**

a 5 kg block with a speed of 3 m/s collides with a 10 kg block that has a speed of 2 m/s in the same direction. After the collision, the 10 kg block is observed to be traveling in the original direction with a speed of 2.5 m/s. a) what is the speed of the 5 kg block ...
*January 13, 2008 by Sarah*

**PreAP Physics**

Pam has a mass of 40Kg and she is at rest on smooth, level, frictionless ice. Pam Straps on a rocket pack. The rocket supplies a constant force for 22m and Pam acquires a speed of 62 m/s. A) What is the magnitude of the force? B) What is Pam's final Kinetic Energy?
*November 30, 2011 by Mandy*

**Physics **

1. What is the kinetic energy of a 0.50 g insect traveling in a straight line at 5.0m/s? a. 6.25j b. 1.25j c. 5.0j d. 250j Is the answer A?? 2. Mechanical energy is defined as the sum of which of the following? a. kinetic, potential and radiant energy b. kinetic, potential and...
*March 14, 2015 by N.*

**Physics**

A boy throws a 4-kg pumpkin at 8m/s to a 40kg girl on roller skates, who catches it. At what speed does the girl then move backwards?
*December 31, 2009 by Aly*

**Physics**

An experimental train has a mass of 1.70e4 kg and is powered across a level track by a jet engine that produces a thrust of 4.90e5 N for a distance of 520 m. a) Find the change in kinetic energy. b) Find the final kinetic energy of the train if it started from rest. c) Find ...
*November 16, 2007 by Einstein*

**Physics**

A block of mass 0.45 kg can slide over a frictionless horizontal surface. It is attached to a spring whose stiffness constant is k = 18 N/m. The block is pulled 38 cm and let go. a)What is its maximum speed? b)What is its speed when the extension is 30 cm? c)At what position ...
*November 5, 2014 by Samantha*

**physics**

I had wrote that was because I was told that in the beginning of the spring being wound the PE=KE. Can I check a concept question, The amount of work required to stop a moving object would be equal to the mass of the object times it intial speed due to mv^2 right. You need to ...
*November 5, 2006 by tatiana*

**phys**

A disk rolls down a slope. It rotational axis is its center of mass. It is rotation at a constant angular speed making 34.0 full revolutions in a time interval of 3.30 s. 1)What is the rotational inertia of the disk if its mass is 11.7 kg, and its radius is 49.6 cm? A=1.44kmg^...
*December 7, 2009 by ami*

**calculus**

(Use the fact that the kinetic energy of a particle of mass "m" moving at a speed "v" is (1/2)m(v^2). Slice object into pieces in such a way that the velocity is approximately constant on each piece.) Q: Find the kinetic energy of a phonograph record of uniform density, mass ...
*October 28, 2012 by mike*

**physics**

a motorbike has a mass of 300kg, and is being ridden along a straight road. The rider sees a traffic queue ahead. He applies the brakes and reduces the speed of the motorbike from 18m/s to 3 m/s. Use this equation to calculate the kinetic energy lost by the motorbike. Kinetic ...
*February 15, 2012 by Teddy Roosevelt*

**physics**

a man 60 kg skating with a speed of 10 m/s collides with 40 kg skater at rest and they cling to eachother. Find the loss in kinetic energy?
*June 4, 2012 by star*

**college physics**

A ball of mass 0.70 kg moving with speed of 1.0 m/s hits a wall and bounces back with the same speed in the opposite direction. What is the change in the ball's kinetic energy?
*February 27, 2011 by craig45*

**Physics**

A car of mass 1,700 kg is initially traveling at a speed of 25 m/s. The driver then accelerates to a speed of 35 m/s over a distance of 500 m. Calculate the change in the kinetic energy of the car.
*July 11, 2012 by Sierra*

**Physics**

A car of mass 1,700 kg is initially traveling at a speed of 25 m/s. The driver then accelerates to a speed of 35 m/s over a distance of 500 m. Calculate the change in the kinetic energy of the car.
*July 11, 2012 by Sierra*

**physics**

12. Which of the following statements is correct for a particle moving in a horizontal circle with constant angular velocity? A. The linear momentum is constant but the kinetic energy varies. B. The kinetic energy is constant but the linear momentum varies. C. Both kinetic ...
*November 1, 2013 by shanza*

**Physics !!!!! HELP PLEASE**

A hand gun fires a 12.0 g bullet at a speed of 400 m/s. What is its kinetic energy? At what speed must a motorcycle of mass 173 kg move to have the same kinetic energy as the bullet? Express your answer in km/h.
*May 22, 2013 by Joeline*

**Physics- check answer please**

1. A 15 kg boy falls out of his bed at a height of 0.50 m. What is the amount of gravitational potential energy lost by the boy? my answer: 74 J 2. What is the speed of a 0.25 kg ball if its kinetic energy is 15 J? my answer: 11 m/s 3. if the speed of an object is tripled and ...
*July 4, 2014 by Liz*

**Physical Science-Can someone check my answers?**

1) The kinetic energy of an object depends on which of the following? A. the object’s mass and direction B. the object’s speed and mass---------- C. the object’s work and direction D. the object’s speed and work 2) In the following situations, which one does not have kinetic ...
*February 18, 2014 by dark1*

**physics**

A bullet with mass m = 5.21 g is moving horizontally with a speed v=367 m/s when it strikes a block of hardened steel with mass M = 14.8 kg(initially at rest). The bullet bounces o the block in a perfectly elastic collision. (a) What is the speed (m/s) of the block immediately...
*December 15, 2011 by Sarah*

**physics**

A particle has a kinetic energy equal to its rest energy. (a) What is the speed of this particle? (b) If the kinetic energy of this particle is doubled, does its speed increase by more than, less than, or exactly a factor of 2? (c) Explain (d) Calculate the speed of a particle...
*April 28, 2012 by martini*

**physics**

suppose an automobile has a kinetic energy of 2900J. when it moves with 3 times the speed, what will be its kinetic energy? answer in the units of joules
*October 28, 2012 by Emily*

**mc questions **

Question # 1-What is the magnitude of the momentum of a particle of mass 2 kg with a speed of 5 m/s? a)2.5 kg m/s b)10 kg m/s c)3 kg m/s d)7 kg m/s Question # 2-If two objects with different masses collide and bounce off each other, the one with the greater mass? a)feels a ...
*May 30, 2012 by macy*

**Physics**

The kinetic energy K of an object of mass m moving at a speed v is defined as K=(1/2)mv^2. It seems reasonable to say that the speed of an object--and, therefore, its kinetic energy--can be changed by performing work on the object. In this problem, we will explore the ...
*April 4, 2010 by mohd*

**physics**

What is the kinetic energy of a car of mass 1900 kg moving at a constant speed of 21 m/s
*September 19, 2011 by gina*

**Physics Question......many thanks**

A projectile is shot directly away from Earth's surface. Neglect the rotation of Earth. (a) As a multiple of Earth's radius RE, what is the radial distance a projectile reaches if its initial speed is one-fifth of the escape speed from Earth? ____ times RE (b) As a multiple of...
*January 15, 2007 by Jessy*

**Physics**

A proton moving with a constant speed has a total energy 2.5 times its rest energy. What is the proton's: a. speed b. kinetic energy
*May 6, 2009 by Anonymous*

**Physics**

A 2.50g bullet, traveling at a speed of 425m/s, strikes the wooden block of a ballistic pendulum. The block has a mass of 270g (a) find the speed of the bullet/block combination immediately after the collision (b) how high does the combination rise above its initial position...
*March 2, 2007 by CJ*

**Physics**

A 1000kg space craft at 500m/s is on a collision course with a 400kg satellite travelling at 700m/s. Their paths are converging at a 45 degree angle. After the collision, they remain locked together. a) calculate their final speed b) calculate the quantity of non-kinetic ...
*December 15, 2010 by Jon*

**Physics**

A 1000kg space craft at 500m/s is on a collision course with a 400kg satellite travelling at 700m/s. Their paths are converging at a 45 degree angle. After the collision, they remain locked together. a) calculate their final speed b) calculate the quantity of non-kinetic ...
*December 15, 2010 by Jon*

**physics**

An ice skater spins about a vertical axis at an angular speed of 15 rad s−1 when her arms are outstretched. She then quickly pulls her arms into her sides in a very small time interval so that the frictional forces due to ice are negligible. Her initial moment of inertia...
*March 15, 2012 by swapnali*

**Physics Problem**

A 3.00-kg mass is fastened to a light spring that passes over a pulley. They pulley is frictionless, and its inertia may be neglected. The mass is released from rest when the spring is unstretched. If the mass drops 10.0cm before stopping, find (a) the spring constant of the ...
*March 21, 2007 by kimberley*

**physics**

A ball attached to the end of a string is whirled on a horizontal circle at constant speed. Consider the linear momentum, total energy, and kinetic energy of the ball throughout its motion. Which of the following statements is true? Both linear momentum and kinetic energy are...
*January 6, 2010 by hilary*

**physics**

an ice skater spins about a vertical axis at an angular speed of 15 rad/s when her arms are outstreched . she then quickly pulls her arms into her sides in a very small time interval so that the frictional force due to ice are negligible.her initial moment of inertia about the...
*February 11, 2012 by ashely*

**Physics**

I need help with part b, c, and d please! A 45 g mass is attached to a massless spring and allowed to oscillate around an equilibrium according to: y(t) = 1.4 * sin( 4 * t ) where y is measured in meters and t in seconds...
*December 3, 2010 by Susan*

**Physics 121 **

A solid sphere of uniform density starts from rest and rolls without slipping a distance of d = 2.7 m down a q = 23° incline. The sphere has a mass M = 4.8 kg and a radius R = 0.28 m. a) Of the total kinetic energy of the sphere, what fraction is translational? KEtran/KEtotal...
*July 14, 2010 by Jay*

**physical science **

Which of the following four bodies has the greatest kinetic energy? a. A body of mass 1 kg moving with speed 1000 m/s. b. A body of mass 2 kg moving with speed 50 m/s c. A body of mass 3 kg moving with speed 50 m/s d. A body of mass 50 kg moving with speed 2 m/s e. A body of ...
*December 15, 2011 by Fonda*

**physics**

An experimental flywheel, used to store energy and replace an automobile engine, is a solid disk of mass 202.0 kg and radius 0.35 m. (a) What is its rotational inertia? (b) When driving at 22.4 m/s (50 mph), the fully energized flywheel is rotating at an angular speed of 3160 ...
*March 22, 2012 by opp*

**physics**

A student holds one end of a string in a fixed position. A ball of mass .2 kg attached to the other end of the string moves in a horizontal circle of radius .5m with a constant speed of 5m/s. How much work is done on the ball by the string during each revolution? a)0 J b).5 J ...
*December 28, 2006 by me*

**Physics**

A car of mass m moving at a speed v1 collides and couples with the back of a truck of mass 3m moving initially in the same direction as the car at a lower speed v2. (Use any variable or symbol stated above as necessary.) (b) What is the change in kinetic energy of the car–...
*March 8, 2014 by Joe*

**Physics**

A car of mass m moving at a speed v1 collides and couples with the back of a truck of mass 3m moving initially in the same direction as the car at a lower speed v2. (Use any variable or symbol stated above as necessary.) (b) What is the change in kinetic energy of the car–...
*March 10, 2014 by Joe*

**Physics**

A car of mass m moving at a speed v1 collides and couples with the back of a truck of mass 3m moving initially in the same direction as the car at a lower speed v2. (Use any variable or symbol stated above as necessary.) (b) What is the change in kinetic energy of the car–...
*March 12, 2014 by Joe*

**Physics**

When a driver applies brakes to keep a car going downhill at constant speed and constant kinetic energy, the potential energy of the dar decreases. Where does this energy go? Where does most of it go with a hybrid vehicle?.
*November 15, 2010 by Melijo*

**Physics**

Two objects moving with a speed v travel in opposite directions in a straight line. The objects stick together when they collide, and move with a speed of v/10 after the collision. (a) What is the ratio of the final kinetic energy of the system to the initial kinetic energy? 1...
*March 3, 2010 by Zane*

**Physics**

When a skydiver jumps from a plane and achieves terminal speed. Which quantity remains constant? (a) Momentum (b) kinetic energy (c) potential energy (d) both a and b (e) both a and c I say kinetic energy, am i right?
*April 4, 2009 by James*

**calculus**

(Use the fact that the kinetic energy of a particle of mass "m" moving at speed "v" is (1/2)m(v^2). Slice objects into pieces in such a way that the velocity us approximately constant on each piece.) Q: Find the kinetic energy of a rod of mass 10kg and length 6m rotating about...
*October 28, 2012 by mike*

**Physics kinetic energy**

Okay the equation for kinetic energy is = 1/2mv^2 so how would i figure this out?? If a semi-truck decreases its speed from 10 m/s to 5 m/s, its new Kinetic Energy is: a)4 times its old Kinetic Energy b)2 times its old Kinetic Energy c)1/2 its old Kinetic Energy d)1/4 its old ...
*October 30, 2010 by Aisumi*

**physics**

A stone is thrown vertically upward. On its way up it passes point A with speed, v and point B, 3 m higher than A, with speed 1/2v. Calculate a) the speed v and b) the max height reached by the stone above point B. I can't find the equation You need to derive the solution in ...
*September 17, 2006 by jenny*

**physics**

A 2.00kg bullet moving at 600m/s strikes a piece of wood at rest on a frictionless table. The bullet sticks in the wood and the combined mass moves slowly down the table. a.) What is the speed of the combined mass after the collision? b.)What is the change in kinetic energy of...
*February 9, 2012 by Alex*

**Physics**

Block B has a mass of 3.40kg and is moving to the left at a speed of 4.20m/s. Block A has a mass of 6.40kg and is moving to the right. The two blocks undergo a perfectly inelastic collision. What should the velocity of the Block A be in order to have the two blocks move to the...
*March 23, 2016 by Emily*

**Physics**

A hollow sphere of radius 0.30 m, with rotational inertia I = 0.080 kg m2 about a line through its center of mass, rolls without slipping up a surface inclined at 19° to the horizontal. At a certain initial position, the sphere's total kinetic energy is 70 J. (a) How much of ...
*October 21, 2009 by Mario*

**physics**

A hollow sphere of radius 0.30 m, with rotational inertia I = 0.072 kg m2 about a line through its center of mass, rolls without slipping up a surface inclined at 25° to the horizontal. At a certain initial position, the sphere's total kinetic energy is 45 J. (a) How much of ...
*January 5, 2011 by Joey*

**Science Check**

1)Two balls having the same mass of 1 kg roll toward each other, each moving at the same speed of 1 m/s. What is the combinded momentum? Would it be 0 kg m/s 2)A 30 kg girl and a 25kg boy face each other on friction free roller blades. The girl pushes the boy who moves away at...
*March 9, 2007 by Abby*

**Physics - Please Help**

Two cars are moving. The first car has twice the mass of the second car but only half as much kinetic energy. When both cars increase their speed by 3.41 m/s, they then have the same kinetic energy. a) What is the original speed of the first car? b)What is the original speed ...
*February 8, 2011 by Emily*

**Physics - Please Help**

Two cars are moving. The first car has twice the mass of the second car but only half as much kinetic energy. When both cars increase their speed by 3.41 m/s, they then have the same kinetic energy. a) What is the original speed of the first car? b)What is the original speed ...
*February 8, 2011 by Emily*

**Physics**

Two cars are moving. The first car has twice the mass of the second car but only half as much kinetic energy. When both cars increase their speed by 3.41 m/s, they then have the same kinetic energy. a) What is the original speed of the first car? b)What is the original speed ...
*February 8, 2011 by Emily*

**Physics**

Two cars are moving. The first car has twice the mass of the second car but only half as much kinetic energy. When both cars increase their speed by 3.41 m/s, they then have the same kinetic energy. a) What is the original speed of the first car? b)What is the original speed ...
*February 8, 2011 by Em*

**Physics**

A 60 kg boy on roller skates moves with a speed of 5 m/s. He runs into a 40 kg girl on skates. Assuming they cling together after the collision, what is their speed?How much kinetic energy was lost in the collision?
*February 21, 2012 by judy*

**Physics**

An object of mass .550kg is lifted from the floor to a height of 3.5m at a constant speed. How much work is done by the lifting force (include units)? b.) How much work is done by the Earth on the object? c.) What is the net work done on the object? d.) What is the change in ...
*December 9, 2012 by Tim*

**physics**

We release an object of mass M at zero speed at a distance of 2*10^6 Km from the center of the earth. What is the speed at which the object hits the earth? G=6.67*10^-11; g= 9.8 m/s; M=5.97*10^24; r=6.3781*10^6 Suppose the mass of the object is M= 500 kg. What is the kinetic ...
*December 27, 2013 by Alice*

**physics**

a body of mass 40kg walk to a step in 40. find the kinetic energy
*June 18, 2014 by godwin*

**physics**

determine the kinetic energy of a boy mass 40kg running with velocity of 3m/s
*March 13, 2016 by energy*

**physics**

A skater spinning with angular speed of 1.5 rad/s draws in her outstretched arms thereby reducing her moment of inertia by a factor a 3. a) Find her final angular speed. b)What is the ratio of her final angular momentum to her initial angular momentum? c) Determine the ratio ...
*December 2, 2010 by Kevin*

**Physics: urgent help needed**

i have a test on monday 1 A beach ball is thrown straight up with a speed of 10m/s from a point 2 m above the ground a) Assuming no air reistance, calculate how far up the ball will go b)At what speed will the ball eventually hit the ground? c) If the air resistance exerts a ...
*April 9, 2011 by deepti*

**Physics**

A solid disk rolls along the floor with a constant linear speed v. (a) Find the fraction of its total kinetic energy that is in the form of rotational kinetic energy about the center of the ball. Krot/Ktotal = ?
*March 8, 2010 by Ace*

**Physics**

Two objects, A and B, have the same kinetic energy. A has a speed that is 12.1 times greater than the speed of B. What is the ratio of the mass of B to the mass of A? I'm not sure how to do this one given... KE_A = KE_B & V_A = 12.1V_B How do I find the ratio of the mass??
*September 26, 2011 by Kaylee*

**physics**

A 9.90-g bullet has a speed of 1.33 km/s. (a) What is its kinetic energy in joules? (b) What is the bullet's kinetic energy if its speed is halved? (c) What is the bullet's kinetic energy if its speed is doubled?
*November 10, 2011 by Jonathan*

**physics**

A 9.90-g bullet has a speed of 1.33 km/s. (a) What is its kinetic energy in joules? (b) What is the bullet's kinetic energy if its speed is halved? (c) What is the bullet's kinetic energy if its speed is doubled?
*November 10, 2011 by Jonathan*

**Physics**

A pitcher claims he can throw a 0.157 kg baseball with as much momentum as a 1.5 g bullet moving with a speed of 1.50 multiplied by 103 m/s. (a) What must the baseball's speed be if the pitcher's claim is valid? m/s (b) Which has greater kinetic energy, the ball or the bullet...
*November 6, 2010 by matt*

**physics**

Joe pushes horizontally on a heavy box across a rough surface at constant speed. Which one of the following statements concerning this situation is false? If Joe stops pushing on the box, the box will stop sliding eventually. If Joe doubles his force on the box, the speed of ...
*June 8, 2014 by Sam*

**physics**

The pendulum shown right has a mass of 0.26 kg and moves to the right from point B to point A. At point B the speed of the mass is 3.2 m/s. (i) What is the change in the gravitational potential energy in the motion from B to A? (ii) What is the mass speed at point A? (iii) If...
*March 8, 2013 by Meder*

**physics**

. When a driver applies brakes to keep a car going downhill at constant speed and constant kinetic energy, the potential energy of the car decreases. Where does this energy go? Where does most of it appear in a hybrid vehicle?
*August 26, 2010 by Anonymous*

**Physics**

When a driver applies brakes to keep a car going downhill at constant speed and constant kinetic energy, the potential energy of the car decreases. Where does this energy go? Where does most of it appear in a hybrid vehicle?
*January 2, 2011 by Sarah*

**Astronomy**

We can calculate the kinetic energy of any moving object with a very simple formula: kinetic energy = 1/2 mv^2 ,where m is the object's mass and v is its velocity or speed. Table Energy Comparisons shows that metabolizing a candy bar releases about 10^6 joules. A- How fast ...
*October 19, 2010 by Isabelle*

**Physics**

A parachutist with mass 79.7 kg jumps from an airplane traveling at a speed vi= 112 km/hr at a height H = 2570 m. He lands with a speed of vf = 5.21 m/s. What is the change in mechanical energy (J) of the earth- parachutist system from just after the jump to just before ...
*June 18, 2011 by Casey *

**Physics**

Equate the increase in potential energy at the higher elevation, M g H, to the decrease in kinetic energy. Make sure you include the kinetic energy of rotation, which is (1/2) I w^2. For a sphere of radius R, V = R w and I =(2/5) I R^2 Therefore KE(rotational) = (1/2)(2/5)M R^...
*March 21, 2007 by drwls*

**physics**

a) compute the kinetic energy in Joules of a 1600kg automibile traveling at 50.0 km/h. By what factor does the kinetic change if the speed is doubled?
*August 22, 2009 by colleen*

**physics**

a bullet of mass 20g is fired into a block of wood of mass 400g . if the bullut and wood move together with speed of 20ms-1 calclate(i) speed with the bullet hits the wood ii the kinetic energy lost iii state the energy changes involed
*August 7, 2015 by kongo.*

**physics**

What speed would a fly with a mass of 0.71 g need in order to have the same kinetic energy as a 1250 kg automobile traveling at a speed of 11 m/s?
*December 1, 2011 by april *

**physics**

What speed would a fly with a mass of 0.61 g need in order to have the same kinetic energy as a 1250 kg automobile traveling at a speed of 11 m/s?
*January 26, 2013 by Brianna Smith*

**physics**

A yo-yo has a rotational inertia of 810 g·cm2 and a mass of 95 g. Its axle radius is 2.6 mm and its string is 100 cm long. The yo-yo is thrown so that its its initial speed down the string is 1.0 m/s. (a) How long does the yo-yo take to reach the end of the string? s (b) As it...
*January 23, 2011 by Help Please!*