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April 19, 2014

April 19, 2014

**Recent Homework Questions About Physics**

Post a New Question | Current Questions

**Physics**

At time 9 s, a car with mass 1400 kg is lo- cated at <94m, 0 m, 30m> and has momentum <4500 kg · m/sec, 0 kg · m/sec,−3000 kg · m/sec> . The car’s momentum is not changing. At time 18 s, find the position of the car: ~d = <dx, dy...
*Thursday, January 23, 2014 at 6:42pm*

**physics**

A model rocket is launched straight upward with an initial speed of 47.7 m/s. It accelerates with a constant upward acceleration of 2.02 m/s2 until its engines stop at an altitude of 157 m. What is the maximum height reached by the rocket? How long after lift off does the ...
*Thursday, January 23, 2014 at 6:34pm*

**physics**

Gave the wrong units, which is J/s; I apologize, I was moving too fast, but the set up is correct.
*Thursday, January 23, 2014 at 6:27pm*

**physics**

Force * time = change of momentum (called "impulse" by the in crowd) 50 * .2 = .5 ( v - 0) v = 20 m/s
*Thursday, January 23, 2014 at 6:18pm*

**physics**

Not quite. momentum=mass*velocity=30 Nt-m/s or J/s
*Thursday, January 23, 2014 at 6:17pm*

**physics**

impulse=momentumchange 50*.2=.5*V solve for V
*Thursday, January 23, 2014 at 6:15pm*

**physics**

find the speed at engine shutdown, and the height of it at that time. H=157 m given vf^2=2ah solve for vf, a, h given. knowing vf at shutdown, what is the height it now goes? speed at the top is zero, so 0=Vfabove^2 + 2ah where a is now -9.8m/s^2, solve for h final height: h+157
*Thursday, January 23, 2014 at 6:15pm*

**physics**

A 0.5 kg soccer ball is kicked with a force of 50 Newtons for 0.2 sec. The ball was at rest before the kick. What is the speed of the soccer ball after the kick?
*Thursday, January 23, 2014 at 6:12pm*

**physics**

A model rocket is launched straight upward with an initial speed of 47.7 m/s. It accelerates with a constant upward acceleration of 2.02 m/s2 until its engines stop at an altitude of 157 m. What is the maximum height reached by the rocket?
*Thursday, January 23, 2014 at 6:11pm*

**physics**

(J) momentum=mass* change in velocity J=3kg*(10m/s-0m/s) since the object started at rest, the initial velocity =0m/s. J=30 J
*Thursday, January 23, 2014 at 6:05pm*

**physics**

A 3kg ball is accelerated from rest to a speed of 10 m/s. What is the ball's change in momentum?
*Thursday, January 23, 2014 at 6:02pm*

**physics**

I assume that the force was applied exactly in the direction of motion change in momentum = 20(8-3) = 100 kg m/s Force = change in momentum /change in time which is another way of saying F = ma 100 N = 100 kg m/s / change in time so change in time = 1 second
*Thursday, January 23, 2014 at 6:00pm*

**physics**

F=ma F=m(âˆ†v/t) Solving for timt (t): t=(mâˆ†v)/F Where t=? m=20.0kg âˆ†v=8m/s-3m/s=5m/s F=100N Solve for t: t=(20kg*5m/s)/100N t=1s
*Thursday, January 23, 2014 at 5:57pm*

**physics**

I assume the momentum is 2000 kg m/s not 2000 kg m V = 2000 1400 V = 2000 v = 1.43 m/s
*Thursday, January 23, 2014 at 5:55pm*

**physics**

A net force of 100 newtons is applied to a 20 kg cart that is already moving at 3 meters per second. The final speed of the cart was 8 m/s. For how long was the force applied?
*Thursday, January 23, 2014 at 5:50pm*

**physics**

A 1,400kg car is traveling in a straight line. Its momentum is equal to 2,000 kg. What is the velocity of the car?
*Thursday, January 23, 2014 at 5:43pm*

**physics**

m v = .25 m (1/2) = .25 m = .5 Kg
*Thursday, January 23, 2014 at 5:36pm*

**physics**

A beach ball rolling in a straight line toward you at a speed of 0.5 m/sec. Its momentum is 0.25kg m/sec. What is the mass of the beach ball?
*Thursday, January 23, 2014 at 5:34pm*

**physics**

change in momentum = 2*.057*52 = 5.928 kg m/s average speed during crush = 52/2 = 26 m/s so time to stop = .028/26 = .0010769 s same time to accelerate back so time force acts = 2*.028/26 = .0021538 seconds force = rate of change of momentum = 5.928/.0021538 = 2752 Newtons
*Thursday, January 23, 2014 at 5:09pm*

**physics**

A tennis ball has a mass of 0.057 kg. A professional tennis player hits the ball hard enough to give it a speed of 52 m/s (about 117 miles per hour.) The ball moves toward the left, hits a wall and bounces straight back to the right with almost the same speed (52 m/s). As ...
*Thursday, January 23, 2014 at 4:55pm*

**Physics-Linear momentum**

kl
*Thursday, January 23, 2014 at 3:46pm*

**College Physics**

I used the definition of acceleration acceleration is how much your velocity changes per second. so here it is the change in speed which is zero to 4500 m/s (1000 times the 4.5 because that was kilometers) in 30 seconds.
*Thursday, January 23, 2014 at 3:11pm*

**College Physics**

can you tell me how you got that? I have a test soon and I seriously dont get it
*Thursday, January 23, 2014 at 2:47pm*

**College Physics**

acceleration = change in velocity/change in time =4500 m/s / 30 s = 150 m/s^2 or about 15 g
*Thursday, January 23, 2014 at 2:44pm*

**College Physics**

Assume that an MX missile goes from rest to a suborbital velocity of 4.50 km/s in 30.0 s (the actual speed and time are classified). What is its average acceleration in m/s2? What is its average acceleration in multiples of g?
*Thursday, January 23, 2014 at 2:41pm*

**college physics**

Are you Daniel Spry?
*Thursday, January 23, 2014 at 2:13pm*

**college physics**

i forgot
*Thursday, January 23, 2014 at 2:08pm*

**college physics**

v = a t 1.6 = 1.2 t t = 1.33 seconds Vi = 1.60 v = Vi + a t 0 = 1.60 + a * 0.8 a = - 2 m/s^2
*Thursday, January 23, 2014 at 1:12pm*

**college physics**

A commuter backs her car out of her garage with a constant acceleration of 1.20 m/s2. (a) How long does it take her to reach a speed of 1.60 m/s? s (b) If she then brakes to a stop in 0.8 s, what is her (constant) deceleration?
*Thursday, January 23, 2014 at 1:07pm*

**physics**

Water drips from a faucet into a flask at the rate of two drops every 3 seconds. A cubic centimeter contains 20 drops. What volume of water, in cubic decimeters will be collected in 1 hour?
*Thursday, January 23, 2014 at 12:13pm*

**physics**

400
*Thursday, January 23, 2014 at 11:50am*

**Physics**

two long parallel wires carrying currents i1 and i2 in opposite directions. What are the magnitude and direction of the net magnetic field at point P? Assume the following values: i1= 10 A, i2= 20 A, and d = 5 cm
*Thursday, January 23, 2014 at 11:37am*

**physics**

A baseball of mass 0.145 kg approaches a bat at 40.0 m/s. After it is hit, the ball leaves the bat at 50.0 m/s directly back. Find the impulse of the bat on the ball.
*Thursday, January 23, 2014 at 10:07am*

**Physics**

dq = 20^10^-6 dx/.1 dF = k (dq)^2/(2x)^2 with x from .025 to .125 so do double integral F on one due to dq on the other dF = dqleft (integral k dq/(2x)^2) from x = .025 to .125 let INT = (integral k dq/(2x)^2) from x = .025 to .125 or dF = INT * integral dqleft from x = -.125 ...
*Thursday, January 23, 2014 at 2:26am*

**physics**

I suppose your original direction was x. The x momentum will not change since there was no force in the x direction. x momentum = .55 * 4 = 2.2 kg m/s I assume z is the horizontal axis perpendicular to x. tsn 23 = Vz/4 so Vz = 1.7 m/s z momentum = .55*1.7 = .934 kg m/s ...
*Thursday, January 23, 2014 at 2:03am*

**Physics**

Two identical teflon rods are 10 centimeters long and rubbed with fur so that they each have a total negative charge of 20 microCoulombs that is uniformly distributed along their length. They are arranged along the same axis, with their ends 5 centimeters apart. What is the ...
*Thursday, January 23, 2014 at 1:54am*

**physics**

20km
*Thursday, January 23, 2014 at 12:49am*

**physics**

A 0.55 kg block of ice is sliding by you on a very slippery floor at 4 m/s. As it goes by, you give it a kick perpendicular to its path. Your foot is in contact with the ice block for 0.0025 seconds. The block eventually slides at an angle of 23 degrees from its original ...
*Thursday, January 23, 2014 at 12:25am*

**Physics**

2
*Wednesday, January 22, 2014 at 11:31pm*

**Physics**

b. 6.53 m/s
*Wednesday, January 22, 2014 at 10:53pm*

**physics**

45
*Wednesday, January 22, 2014 at 10:40pm*

**physics**

q
*Wednesday, January 22, 2014 at 10:38pm*

**physics**

d= vi*t+1/2 a t^2 vi is given, a is given, in the last second find d for t=5 seconds, then t=4 seconds, the difference is the displacment in the last second.
*Wednesday, January 22, 2014 at 10:33pm*

**physics**

a. it has mg(1.50) PE less that at the ceiling b. it has mg(3.36-1.50) PE more than at floorlevel. c. at the same mpoint it has the same PE
*Wednesday, January 22, 2014 at 10:29pm*

**physics**

A 1.70 kg ball is attached to a ceiling by a 1.50 m long string. The height of the room is 3.36 m. The acceleration of gravity is 9.81 m/s2 . What is the gravitational potential energy associated with the ball relative to a) the ceiling? Answer in units of J b) the floor? ...
*Wednesday, January 22, 2014 at 10:22pm*

**physics**

Atom Ant is traveling with an initial velocity of 20.0 cm/s. He begins to accelerate at a rate of 8.00 cm/s2 for 5.00 s. What is his total displacement in the 5.00 second interval? What is his displacement in the last second?
*Wednesday, January 22, 2014 at 10:17pm*

**Physics**

18.085 m/s
*Wednesday, January 22, 2014 at 10:07pm*

**Physics**

initial KE=final PE 1/2 m 22.5^2=m g h solve for h. time in air: hf=hi+vi*t-4.9t^2 hf=hi and vi is given, solve for t.
*Wednesday, January 22, 2014 at 9:17pm*

**Physics**

a=5/4.5 m/s^2 distance=1/2 a*4.5^2 + (a*4.5)*4.5 solve for distance.
*Wednesday, January 22, 2014 at 9:16pm*

**Physics**

d=1/2 a t^2 vf=a*t
*Wednesday, January 22, 2014 at 9:14pm*

**Physics**

A tennis ball is thrown up with an initial speed of 22.5m/s. It is caught at the same distance above the ground. A) how high does the ball rise B) how long does the ball remain in the air?
*Wednesday, January 22, 2014 at 9:14pm*

**physics**

The answer is supposed to be 34m..
*Wednesday, January 22, 2014 at 9:02pm*

**physics**

The answer is supposed to be 34m..
*Wednesday, January 22, 2014 at 9:02pm*

**physics**

What is the mass of the object?
*Wednesday, January 22, 2014 at 8:50pm*

**Physics**

An airplane starts from rest and accelerates at a constant rate if 3.00m/s^2 for 30.0s before leaving the ground. A)How far did it move? B) how fast was it going when it took off?
*Wednesday, January 22, 2014 at 8:32pm*

**Physics**

A car traveling at 20m/s when the driver sees a child standing in the road. He takes 0.80s to react, then steps on the brakes and slows at 7.0m/s^2. How far does the car go before it stops?
*Wednesday, January 22, 2014 at 8:30pm*

**Physics **

A bike first accelerates from 0.0m/s to 5.0m/s in 4.5s, then continues at this constant speed for another 4.5s. What is the total distance traveled by the bike?
*Wednesday, January 22, 2014 at 8:29pm*

**Physics **

A bike first accelerates from 0.0m/s to 5.0m/s in 4.5s, then continues at this constant speed for another 4.5s. What is the total distance traveled by the bike?
*Wednesday, January 22, 2014 at 8:29pm*

**Physics**

bullet momentum up = .005 * 320 = 1.6 kg m/s If the momentum of the block down is 1.6 then they both come to a stop Vdown = g t momentum down = m g t so when m g t = 1.6, they stop .5*9.81*t = 1.6 t = .326 seconds how high is the block then? h = 15 - (1/2)g t^2 h = 15 - 4.9(....
*Wednesday, January 22, 2014 at 6:41pm*

**Physics**

48000/3600 = 13.33 m/s 35000/3600 = 9.72 m/s d1 = d + 10 d = 9.72 t d1 = 13.33 t = d + 10 so 9.72 t + 10 = 13.33 t
*Wednesday, January 22, 2014 at 6:30pm*

**Physics**

(1/2) k x^2 (1/2)(5.4)(3.64-2.63)^2 2.75427 Joules
*Wednesday, January 22, 2014 at 6:25pm*

**Physics**

If a car travelling 48km per hour and is 10 metres behind a car travelling 35km per hour, how much time before it catches up?
*Wednesday, January 22, 2014 at 6:24pm*

**Physics**

A spring with a force constant of 5.4 N/m has a relaxed length of 2.63 m. When a mass is attached to the end of the spring and allowed to come to rest, the vertical length of the spring is 3.64 m. Calculate the elastic potential energy stored in the spring. Answer in units of ...
*Wednesday, January 22, 2014 at 6:19pm*

**Physics**

F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F=6.67•10⁻¹¹•0.005•10/0.25=...
*Wednesday, January 22, 2014 at 5:07pm*

**Physics **

Two spheres with masses of 5.00 g and 10. kg respectively are .500 m apart. calculate the force of attraction between them.
*Wednesday, January 22, 2014 at 4:19pm*

**Physics**

sfsf
*Wednesday, January 22, 2014 at 3:51pm*

**Physics**

A 0.5 kg wooden block is dropped from a height of 15 m. At what height must a 5g bullet be traveling upward strike the block in order to momentarily stop its fall? Assume that the time required for the bullet to come to rest in the block in negligibly short, that no internal ...
*Wednesday, January 22, 2014 at 3:43pm*

**physics**

A ray of light goes through the centre of a semicircular glass disk, n = 1.58, and onto a wall (x = 19.4 cm, y = 5.06 cm). What is the incident angle, θ?
*Wednesday, January 22, 2014 at 3:21pm*

**physics**

A boy of mass 50kg runs up a set of stairs of total height of 3.0m.find the work done against gravity
*Wednesday, January 22, 2014 at 2:39pm*

**physics(online)**

Use F=G(m1m2/r^2)
*Wednesday, January 22, 2014 at 2:15pm*

**Physics**

Use conservation of momentum and conservation of kinetic energy (since it's an elastic collision.)
*Wednesday, January 22, 2014 at 2:12pm*

**physics**

3
*Wednesday, January 22, 2014 at 2:09pm*

**physics**

Which of the following was explained by the Bohr atom? 1. atomic spectra 2. the fact that most of the mass of an atom is in the nucleus 3. nuclear fission 4. the photoelectric effect
*Wednesday, January 22, 2014 at 2:02pm*

**physics**

8.01 question ?
*Wednesday, January 22, 2014 at 12:02pm*

**physics**

How far would a car of 126 horse power have gone when it attains a speed of 70 km/hour going up the hill with 15 degrees incline. Total weight of the car is 1338 kg
*Wednesday, January 22, 2014 at 11:31am*

**physics**

10 km
*Wednesday, January 22, 2014 at 11:10am*

**Physics**

i dont know... teachers even cant... lol
*Wednesday, January 22, 2014 at 10:47am*

**physics**

A man walks 10km due south. The displacement of the man from the initial position is
*Wednesday, January 22, 2014 at 6:37am*

**Physics PLEASE HELP ASAP :)**

fasdfa
*Wednesday, January 22, 2014 at 4:18am*

**Physics**

The goblins fists cut through the air and connects with the dwarfs face in an elastic collision. The goblins fists each weigh 2kg and the dwarfs head weighs 5kg. What is the kinetic energy imparted to the dwarfs face by the goblins fists if the goblins fists had an initial ...
*Wednesday, January 22, 2014 at 2:50am*

**Physics**

A lamp is 4m from wall. Calculate the focal length of a concave mirror which forms a five time magnified image of lamp on wall. How far from wall must the mirror be placed?
*Wednesday, January 22, 2014 at 2:07am*

**Physics**

an object 2.6 cm high is 24cm from concave mirror whose radius of curvature is 16cm. Determine the location of its image. the answer is 12cm in front of mirror. I want to know what to get this. What steps and which formulas are used? please help
*Wednesday, January 22, 2014 at 1:26am*

**physics**

A wave is described by the equation y = 3sin(5t - 3x + 2ð). What is the velocity of the wave?
*Wednesday, January 22, 2014 at 1:08am*

**physics**

Two ping pong balls each have a mass of 1.4 grams and carry a net charge of 0.450uC. one ball is held fixed. at what height should the second ball be placed directly above the fixed ball if it is to remain at rest there?
*Wednesday, January 22, 2014 at 12:31am*

**physics**

why no answer
*Tuesday, January 21, 2014 at 11:36pm*

**Physics**

help!!!
*Tuesday, January 21, 2014 at 11:06pm*

**physics**

d = 350 100 = 250 m. = Braking distance. a=(V^2-Vo^3)/2d=(0-60^2)/500=-7.2 m/s^2
*Tuesday, January 21, 2014 at 10:23pm*

**physics(online)**

Find the change in the force of gravity between two planets when distance between them is decreased by 12
*Tuesday, January 21, 2014 at 10:20pm*

**Physics**

so 81.34?
*Tuesday, January 21, 2014 at 9:39pm*

**physics**

Vw=(10kg-4kg) * 1m^3/1000kg = 0.006 m^3 = Vol. of water displaced = Vol. of the object submerged. Do = 6kg/0.006m^3 = 1000kg/m^3 = Density of the object. = Density of water(Dw). Do/Dw * Vo = 0.006 m^3 (1000/1000) * Vo = 0.006m^3 Vo = 0.006 m^3 = Vol. of the object. So the ...
*Tuesday, January 21, 2014 at 9:35pm*

**physics**

v= g*time
*Tuesday, January 21, 2014 at 9:32pm*

**Physics**

v=g*time
*Tuesday, January 21, 2014 at 9:31pm*

**physics**

oops, displacment is 77.5 laps, so he net displacment is the pool length. Avg velocity = displacement/time
*Tuesday, January 21, 2014 at 9:31pm*

**Physics**

A rock is dropped from rest. How fast is it going after it has been falling for 8.3 s?
*Tuesday, January 21, 2014 at 9:31pm*

**physics**

If you have swam one lap in a swimming pool, that means you have swam from one end to the other and back. In 1.5 h, a swimmer makes exactly 77 laps in a swimming pool that is 27 m long. Determine the distance the swimmer traveled, the total displacement of the swimmer, the ...
*Tuesday, January 21, 2014 at 9:25pm*

**physics**

I put 5.17km/h because it asks for it in km also i put 0 for avg velocity and that's wrong
*Tuesday, January 21, 2014 at 9:16pm*

**physics**

avg speed=distancetraveled/timetotal avg velocity=displacement/time=0/time
*Tuesday, January 21, 2014 at 9:07pm*

**Physics**

net force=(outside pressure-1atm)areawindow so, the pressure of the water weight from above is... P= weightwater/area + atmospheric pressure above = g*density*heigh*area/area+ 1atm = g*density*15m + 1atm = 9.8*15*1030 + 101.3kpa
*Tuesday, January 21, 2014 at 9:06pm*

**physics**

I just have the the total distance traveled. 7750
*Tuesday, January 21, 2014 at 9:05pm*

**physics**

and your thinking is...? I will be happy to check your work.
*Tuesday, January 21, 2014 at 8:58pm*

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