Friday

April 18, 2014

April 18, 2014

**Recent Homework Questions About Physics**

Post a New Question | Current Questions

**physics**

A 10^4 kg train moving at 20m/s stops in a distance of 500m. Calculate the force applied by the train's braking system.
*Friday, March 14, 2014 at 8:56pm*

**physics**

When rolling along the felt on the billiard table, the ball experiences a frictional force of 0.2 N. a. What is the deceleration of the ball on the felt? b. How far will the ball roll before stopping? c. Explain this in terms of Newtons first law of motion.
*Friday, March 14, 2014 at 8:52pm*

**Physics**

a)work=mgh so work=(3.4kg)(9.8m/s^2)(1.4)=47J
*Friday, March 14, 2014 at 8:51pm*

**physics**

A force of 15 N (delivered by a cue) acts on a billiard ball for 0.01 s. Find the magnitude of the a. acceleration of the ball b. final speed of the ball c. distance over which the cue was in contact with the ball
*Friday, March 14, 2014 at 8:46pm*

**physics**

V = Vo + g*t = 0 + 10*1=10 m/s. T = 1s. d = Vo*t + 0.5g*t^2 d = 10*1 + 5*1^2 = 15 m.
*Friday, March 14, 2014 at 8:46pm*

**physics**

My answer is B also.
*Friday, March 14, 2014 at 8:28pm*

**Physics**

P = 16/12 = 1.333 s.
*Friday, March 14, 2014 at 8:22pm*

**physics**

.l.
*Friday, March 14, 2014 at 8:12pm*

**Physics**

d = V*t = 305 m. V*(1.85/2) = 305 V = 329.7 m/s.
*Friday, March 14, 2014 at 8:05pm*

**Physics**

Two cars are parked on a street. A third car hits the back of the second car and causes all of the cars to move. (Ignore the distance between the cars). Calculate: (a)The acceleration of the whole system; (b)the net force on each car; (c)the contact force that each car exerts ...
*Friday, March 14, 2014 at 7:57pm*

**Physics**

I suspect Flove is in Newtons, not in meters integral F dx from 0 to 2.6 (2/3) x^3 + (3/4) x^4 zero at 0 so just evaluate for x = 2.6 11.71 + 34.27 = 46 Newtons
*Friday, March 14, 2014 at 7:56pm*

**physics**

a = (V-Vo)/t = (-8-16)/0.04 = -600 m/s^2 F = m*a = 0.2 * (-600) = -120 N.
*Friday, March 14, 2014 at 7:28pm*

**physics**

Xo = 0.9 m/s? D = Xo*t = 0.9m/s * 0.4s = 0.36 m.
*Friday, March 14, 2014 at 7:13pm*

**Physics**

A mountain climber dangles his water bottle and feels the bottle makes an angle of 25 degrees with respect to the vertical line. If his acceleration takes 18 seconds, calculate the speed of the climber.
*Friday, March 14, 2014 at 7:06pm*

**physics**

B. 10 m/s, North.
*Friday, March 14, 2014 at 7:01pm*

**Physics**

For a) I got -4.11 m/s. (This is correct). I am having trouble finding b) though. I only have 2 more attempts and if anyone could help, I would appreciate it.
*Friday, March 14, 2014 at 5:06pm*

**Physics**

I apologize, I meant this for my other question. I got 22.5 for this, but it was wrong. If someone can at least show calculations in getting this, I would appreciate it.
*Friday, March 14, 2014 at 5:04pm*

**Physics**

For a) I got the answer -4.11 m/s. (This is correct) I am having trouble finding b) though.
*Friday, March 14, 2014 at 5:03pm*

**Physics**

Two lovebirds are held together by a stange force called love. Physicists recently discovered the functional form of love (a conservative force) as a function of distance, for lovebirds. Flove(x)=2x^2+3x^3. (units in meters) Assuming they start off next to each other, how much...
*Friday, March 14, 2014 at 4:24pm*

**Physics**

A particle leaves the origin with an initial velocity v=(3.68i) m/s and a constant acceleration a=(-3.33i-3.72j)m/s^2. When the particle reaches its maximum x coordinate, what are (a) its velocity, (b) its position vector?
*Friday, March 14, 2014 at 3:45pm*

**Physics**

The acceleration of a particle moving only on a horizontal xy plane is given by a=5ti+6tj, where a is in meters per second-squared and t is in seconds. At t=0, the position vector r=(19.0m)i+(39.0m)j locates the particle, which then has the velocity vector v=(5.70m/s)i+(3.40m/...
*Friday, March 14, 2014 at 3:43pm*

**Physics**

Assume a spring has an un-stretched length Xo. Write an expression for the elastic potential energy of the spring in terms of the position of the end of the spring X and its spring constant K.
*Friday, March 14, 2014 at 3:06pm*

**urgent (physics)**

A 2 kg brick falls at 5.1 m/s from a height of 6 m above a spring that has a spring constant of 47 N/m. The brick strikes and compresses the spring until it stops moving. Ignore friction effects. How much is the spring compressed by the brick? Assume that there is no Eg after ...
*Friday, March 14, 2014 at 2:43pm*

**Physics**

A skater with an initial speed of 5.90 m/s stops propelling himself and begins to coast across the ice, eventually coming to rest. Air resistance is negligible. (a) The coefficient of kinetic friction between the ice and the skate blades is 0.125. Find the deceleration caused ...
*Friday, March 14, 2014 at 1:24pm*

**I need help (Physics)**

PE = mgh = 28*9.8*159 KE = 1/2 mv^2 = 1/2 * 28 * 31.3^2 Because of friction, not all of the PE changed to KE. Subtract to see how much energy was lost.
*Friday, March 14, 2014 at 1:13pm*

**Physics**

A car starts from rest and moves with uniform acceleration of 0.3 meter per second. After 30 second, find the velocity of the car and distance covered?
*Friday, March 14, 2014 at 1:06pm*

**Physics**

A 2 kg brick falls at 5.1 m/s from a height of 6 m above a spring that has a spring constant of 47 N/m. The brick strikes and compresses the spring until it stops moving. Ignore friction effects. How much is the spring compressed by the brick? Assume that there is no Eg after ...
*Friday, March 14, 2014 at 12:31pm*

**Physics**

A 2 kg brick falls at 5.1 m/s from a height of 6 m above a spring that has a spring constant of 47 N/m. The brick strikes and compresses the spring until it stops moving. Ignore friction effects. How much is the spring compressed by the brick? Assume that there is no Eg after ...
*Friday, March 14, 2014 at 12:28pm*

**physics**

A chemist is working with a 4.50 mol sample of an ideal gas. The internal energy of the sample is known to be 14,900 J. What is the average kinetic energy of each gas molecule?
*Friday, March 14, 2014 at 12:21pm*

**I need help (Physics)**

A 28 kg ball initially at rest rolls down a 159 m hill. When the ball reaches the bottom it is traveling at 31.3 m/s. How much energy is dissipated by friction on the ball?
*Friday, March 14, 2014 at 12:02pm*

**physics**

A 15.7 kg block is at rest on a ramp, whose angle is 12.1 degrees from the horizontal. How much Normal Force is acting on the block?
*Friday, March 14, 2014 at 11:25am*

**Physics**

A 28 kg ball initially at rest rolls down a 159 m hill. When the ball reaches the bottom it is traveling at 31.3 m/s. How much energy is dissipated by friction on the ball?
*Friday, March 14, 2014 at 11:23am*

**physics-impulse**

A tennis ball of mass m = 0.068kg and speed v = 21m/s strikes a wall at a 45∘ angle and rebounds with the same speed at 45 What is the magnitude of the impulse given to the ball?
*Friday, March 14, 2014 at 11:22am*

**Physics**

Stan the strongman lifts a 524 kg dumbbell from the floor to 1.69 meters above the floor at a constant velocity. How much energy does it take Stan to lift the dumbbell?
*Friday, March 14, 2014 at 11:21am*

**Physics**

A stream of water flows through a small hole at depth h = 10 cm in a tank holding water to height H =40 cm. At what distance x (in cm) does the stream strike the floor? (Neglect air resistance).
*Friday, March 14, 2014 at 10:51am*

**Physics**

A rope is wound round a fixed cylinder of radius r so as to make n complete turns . Show that if one end of the rope is held by a force f, a force f e^2(pi)nu must be applied to the other end to produce slipping,where u is the coeff. of friction between rope and cylinder.
*Friday, March 14, 2014 at 10:50am*

**physics**

H
*Friday, March 14, 2014 at 10:17am*

**physics**

initial Ke calculate final Ke, calculate ke lost=initial-final fractction lost=kelost/keinitial
*Friday, March 14, 2014 at 9:56am*

**physics**

let h be the heigth from ground. hf=hi+10*t-4.9t^2 calculate hf-hi Nowhere in this planet is g=10m/s^2. Shame on your instructor for assuming you are so stupid that you can't use g=9.8m/s^2
*Friday, March 14, 2014 at 9:55am*

**physics**

Why would I take this test for you?
*Friday, March 14, 2014 at 9:52am*

**physics**

use conservation of momentum. masspackage*velocitypackage+totalmassinboart*velocityboat=0 solve for velocityboat.
*Friday, March 14, 2014 at 9:52am*

**Physics**

a. vf=vi+at where a=force/mass solve for time t b. vf^2=vi^2+2ad where a=brakingforce/mass
*Friday, March 14, 2014 at 9:46am*

**Physics**

draw the figure. Let the 42deg be on the right. the horizontal components are equal or Tl*cos37=Tr*cos42 the vertical components add to the weight of the light. 2.3*9.8=Tlsin37+Trsin42 two equaions, two unknowns, solve for Tension left and Tension right.
*Friday, March 14, 2014 at 9:45am*

**Physics**

A traffic light is hanging from two cables tilted at 37 and 42 degrees. If it has a mass of 2.3 kg find the tension in each cable.
*Friday, March 14, 2014 at 9:37am*

**Physics**

A freight train has a mass of 4.78 * 10^7 kg. the locomotive provides a force of 1.3 * 10^6 N and the brakes provide a force of -3.2 * 10^3 N. 1. How long will it take for the train to accelerate to it's maximum speed of 15 m/s? 2. The train accidentally stumbles into an ...
*Friday, March 14, 2014 at 9:36am*

**physics**

A child in a boat throws a 5.15-kg package out horizontally with a speed of 10.0 m/s. The mass of the child is 24.2kg and the mass of the boat is 33.2kg . Calculate the velocity of the boat immediately after, assuming it was initially at rest.
*Friday, March 14, 2014 at 9:02am*

**physics**

What is the gravitational field strength at a height h above the surface of the Earth? R is the radius of the earth gR2(R+h)2 gR(R+h) g(R−h)R g(R−h)2R2 2 The instrument used for experimental determination of the value of the universal gravitational constant G is ...
*Friday, March 14, 2014 at 7:24am*

**physics**

An object is thrown upward from the edge of a tall building with a velocity of 10 m/s. Where will the object be 3 s after it is thrown? Take g=10ms−2
*Friday, March 14, 2014 at 7:16am*

**Physics**

I did not understand the part of the normal force..how did you gt that?
*Friday, March 14, 2014 at 2:33am*

**physics**

Thanks a lot...and how do you find out the work required to turn the cylinder through one complete turn under these conditions?
*Friday, March 14, 2014 at 2:11am*

**physics**

Croquet ball A moving at 8.0m/s makes a head on collision with ball B of equal mass and initially at rest. Immediately after the collision ball B moves forward at 7.1m/s . What fraction of the initial kinetic energy is lost in the collision?
*Friday, March 14, 2014 at 2:02am*

**Physics**

sorry the subject is Physics
*Friday, March 14, 2014 at 12:26am*

**Physics**

A 295kg box is pulled at a constant speed by the little engine. The box moves a distance of 2.8 m across the horizontal surface. (μ=.20) How much energy is transferred by the engine? (How much WORK is done?)
*Friday, March 14, 2014 at 12:17am*

**physics**

PEmax = mg*hmax = mg*4.07 J. Change = 0-mg*4.07 = -3900 mg = 958.2 N. = Wt. of the vaulter.
*Thursday, March 13, 2014 at 11:33pm*

**physics**

Idk
*Thursday, March 13, 2014 at 10:21pm*

**physics**

Fh = 151 Hz Vr = 28.7 m/s Vs = 343 m/s Fr = ((Vs+Vr)/(Vs-Vh)) * Fh Fr = ((343+28.7)/(343-0)) * 151 Hz = (371.7/343) * 151 = 163.6 Hz = Freq. heard by the receiver(Passenger).
*Thursday, March 13, 2014 at 10:11pm*

**Physics**

P = F*d/t = 0.5 * 2.1/1.1 = 0.955 J/s = 0.955 Watts.
*Thursday, March 13, 2014 at 9:42pm*

**Physics**

height = x sin theta potential energy = m g h = m g x sin theta assuming x is zero at the bottom and positive up ramp potential energy + kinetic energy = total energy = constant if ignoring friction potential = m g x sin theta kinetic = (1/2) m v^2 sum is constant so as x ...
*Thursday, March 13, 2014 at 9:41pm*

**Physics!**

PE = F*h = mg*h = 1.2*9.8 * 4 = 47.04 J.
*Thursday, March 13, 2014 at 9:10pm*

**physics**

m = 85 kg? V = 450 L. V = 450L * 1000cm^3/L = 450,000cm^3 D = 85,000g/450,000cm^3 = 0.189 g/cm^3. Mass = 300cm^3 * 0.189g/cm^3 = 56.67 g = 0.0567 kg.
*Thursday, March 13, 2014 at 9:01pm*

**physics**

00
*Thursday, March 13, 2014 at 6:55pm*

**physics**

A coin is dropped from a height of 40 meters. How fast is the coin traveling after 3 seconds?
*Thursday, March 13, 2014 at 6:33pm*

**Physics**

Assume a spring has an un-stretched length Xo. Write an expression for the elastic potential energy of the spring in terms of the position of the end of the spring x and its spring constant k.
*Thursday, March 13, 2014 at 6:20pm*

**Physics**

Consider the gravitational potential, kinetic, and total mechanical energies of a cart moving down an inclined ramp. (Also, let gravitational potential energy be defined to be zero when the cart is at the bottom of the ramp. A. Write an expression for the gravitational ...
*Thursday, March 13, 2014 at 6:19pm*

**science pls help**

Looks like you need to brush up on one of the most basic and useful identities in mechanics: F = ma F(N) = m(kg) * a(m/s^2) 1 N = 1 kg-m/s^2 So, with that in mind, #1: F = ma = 40kg * 10m/s^2 = 400 kg-m/s^2 = 400N #2: F = ma = 60kg * 2m/s^2 = 120N Note that you can eliminate ...
*Thursday, March 13, 2014 at 5:31pm*

**physics**

distance flown if level = d tan 78.6 = 5900/d d = 1190 meters in ten seconds so 119 meters/second
*Thursday, March 13, 2014 at 5:31pm*

**physics**

A plane is found by radar to be flying 5.9 km above the ground. The angle of elevation from the radar to the plane is 78.6°. Ten seconds later, the plane is directly over the station. Find the speed of the plane, assuming that it is flying level.
*Thursday, March 13, 2014 at 5:04pm*

**Needs plant biologist**

Hey, my degree is in Physics :)
*Thursday, March 13, 2014 at 4:57pm*

**physics**

take an element d A where A is the angle around the cylinder tension T to the left tension T + dT to the right then normal force toward center = (T+dT)(dA/2) + T(dA/2) = T dA for small dA so friction force = mu T dA so dT = mu T dA dT/T = mu dA ln T = mu A T = c e^mu A at A = ...
*Thursday, March 13, 2014 at 4:45pm*

**physics**

May I please know how do you do it?first of all how to prove the first part?
*Thursday, March 13, 2014 at 4:11pm*

**Physics**

A rope is wound round a fixed cylinder of radius r so as to make n complete turns . Show that if one end of the rope is held by a force f, a force f e^2(pi)nu must be applied to the other end to produce slipping,where u is the coeff. of friction between rope and cylinder. Find...
*Thursday, March 13, 2014 at 4:07pm*

**physics**

this question is of ohysics
*Thursday, March 13, 2014 at 4:06pm*

**physics**

How do you solve it?
*Thursday, March 13, 2014 at 4:05pm*

**physics**

A rope is wound round a fixed cylinder of radius r so as to make n complete turns . Show that if one end of the rope is held by a force f, a force f e^2(pi)nu must be applied to the other end to produce slipping,where u is the coeff. of friction between rope and cylinder. Find...
*Thursday, March 13, 2014 at 3:58pm*

**Physics**

density = 1000 kg/m^3 volume = 26 * 32 * 3 = 2496 m^3 so mass = 2.496*10^6 kg so weight = 9.81*mass = 24.486 *10^6 N = 2.45*10^7 N
*Thursday, March 13, 2014 at 2:47pm*

**Physics**

A swimming pool has dimensions 26 m x 32 m and a flat bottom. When the pool is filled to a depth of 3 m with fresh water, what is the total force due to the water on the bottom?
*Thursday, March 13, 2014 at 2:42pm*

**Physics**

specific heat of fresh water = 4186 J/kgdegC heat in = 4186*100* 20 = 8372,000 Joules = 8372 kJ
*Thursday, March 13, 2014 at 2:00pm*

**Physics**

If you wish to warm 100 kg of water by 20° C for your bath, show that 8370 kJ of heat is required.?
*Thursday, March 13, 2014 at 1:43pm*

**physics**

Amar has a weight of 600N on Earth . what is his weight on mercury?
*Thursday, March 13, 2014 at 1:09pm*

**Physics**

weight down = m g = 97*9.81 = 952 N friction up = 810 N net force down = 142 N 142 = 97 a a = 1.46 m/s^2 v = a t 3.7 = 1.46 t at bottom so t = 2.54 seconds d = (1/2) a t^2 d = .5 (1.46)(2.54)^2 d = 4.69 meters long
*Thursday, March 13, 2014 at 11:56am*

**Physics**

A 97 kg person slides down a pole, just for fun. The pole has a frictional force of 810 N and the speed of the person at the bottom of the pole is 3.7 meters per second. How long was the pole?(? m)
*Thursday, March 13, 2014 at 11:34am*

**physics**

The charge carried by one electron is e = -1.6 × 10-19 C. The number of electrons necessary to produce a charge of -1.0 C is:
*Thursday, March 13, 2014 at 9:21am*

**physics**

A brass ball weighs 270gram in air and when it was immersed in water,it displaced 30 ml of water .how much will the ball weigh in water?
*Thursday, March 13, 2014 at 8:33am*

**physics**

y = A sin 2 pi f t y"=-A(2 pi f)^2sin 2pift = -(2 pi f)^2 y -k y = m y" - k y = - m (2 pi f)^2 y (2 pi f)^2 = k/m f = (1/2pi)sqrt(k/m) f = (1/2pi) sqrt (200/50) f = 1/pi = .3183098852 Hz call it 0.318 Hz
*Thursday, March 13, 2014 at 5:30am*

**Physics**

5*200 = 1,000 watts = 1 kw 1 * 8 = 8 kw hr 8 cents/kw h * 8 kw h = 64 cents every 8 hours
*Thursday, March 13, 2014 at 4:59am*

**Physics**

Ken has five 200W security lights on outside of home. How much energy do the security lights use in 8 hrs? If the cost of electricity is 8 cents per kWh,what is the cost of operating the security lights ? Please help I'm not sure which formula to use?
*Wednesday, March 12, 2014 at 11:45pm*

**physics**

A boy with a mass of 50 kg is hanging from a spring with a spring constant of 200 N/m. With what frequency does the boy bounce up and down?
*Wednesday, March 12, 2014 at 11:39pm*

**physics**

9
*Wednesday, March 12, 2014 at 10:10pm*

**physics**

F*d = 25 J. F * 0.13 = 25 F = 192.3 N. k = 192.3N/0.13m = 1479N/m
*Wednesday, March 12, 2014 at 10:04pm*

**Physics**

b. The truck.
*Wednesday, March 12, 2014 at 9:55pm*

**physics**

What are the given angles?
*Wednesday, March 12, 2014 at 9:06pm*

**PHYSICS HELP!**

do ypou work
*Wednesday, March 12, 2014 at 8:02pm*

**physics**

false
*Wednesday, March 12, 2014 at 7:57pm*

**physics**

,k
*Wednesday, March 12, 2014 at 7:43pm*

**physics**

a. Zero.
*Wednesday, March 12, 2014 at 7:27pm*

**physics**

.
*Wednesday, March 12, 2014 at 7:24pm*

**Physics**

6.55 10-7 W/m2
*Wednesday, March 12, 2014 at 6:53pm*

**Physics**

ok, that is may angle A so plug sin 59.2 and cos 59.2 in but check my algebra first
*Wednesday, March 12, 2014 at 6:41pm*

**Physics**

Do it all over very carefully is all I can suggest.
*Wednesday, March 12, 2014 at 6:37pm*

**Physics**

i cant seem to find the error but i still cant get the correct answer
*Wednesday, March 12, 2014 at 6:31pm*

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