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Physics > Energy & Momentum > Flashcards

Energy & Momentum Flashcards

0
Q

List the three conditions where no work is done.

A
  • 0 Force
  • 0 Displacement
  • Displacement perpendicular to force
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1
Q

A child pulls a wagon with a 21 N force over a displacement of 3.2m. How much work has been done?

A

67.2 J

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2
Q

A girl pulls a wagon while completing her paper route. If she applies a force of 80N, but the wagon handle makes an angle of 35 degrees with the horizontal, how much work has been done over one block (350m)?

A

2.3x10^4 J

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3
Q

A spring is hung from the ceiling. If the mass of 0.55kg causes it to extend 2.0cm, what is the force constant of the spring?

A

270 N/m

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4
Q

A spring (k=90N/m) attaches a 1.5kg block to a wall on a frictionless surface:

a) What force does the block experience if it pulled 20cm from rest?
b) What is the acceleration of the block if it is released?
c) Say this spring is attached to the ceiling and pulled down 20cm. What is its new acceleration?

A

a) 18N
b) 12 m/s^2
c) 2.2 m/s

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5
Q

A bungee jumper of mass 64.5kg is standing on a platform 48.0m above a river. The length of the un-stretched bungee cord is 10.1m and k=65.5N/m. If the jumper starts at rest, what is her speed 12.5m above the river?

A

6.4 m/s

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6
Q

An apple, m = 100g, is attached to a vertical spring with a force constant of 15.5N/m. The apple is held so the spring is un stretched. Using conservation of energy:

a) How far will the spring stretch if the apple is released?
b) How much elastic potential energy is stored in the spring when the apple has fall 11cm?
c) What is the speed of the apple when it has fallen 11cm?

A

a) 0.126m
b) 0.094 J
c) 0.53 m/s

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7
Q

A spring connects a mass to a wall. The frictionless system is put into SHM with a maximum energy of 5.64J. If m=0.128kg and k=244N/m.

a) What is the amplitude of the vibration?
b) What is the maximum speed of the mass?
c) What is its speed when it is 15.5cm from the equilibrium?

A

a) 21.5cm
b) 9.39 m/s
c) 6.51 m/s

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8
Q

A block attached to a horizontal spring with k=75 N/m undergoes SHM with an amplitude of 0.15m. If the speed of the block is 1.7m/s when the displacement is 0.12m from equilibrium, what is the mass of the block?

A

0.21 kg

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9
Q

A bullet travelling at 900 m/s [W] has a momentum of 4.5 Ns. What is its mass?

A

5 g

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10
Q

A baseball of mass of 0.152kg travelling at 37.5m/s [E] collides with a baseball bat. The collision lasts for 1.15ms. After the collision, the baseball travels at 49.5m/s [W]. What is the force of the bat on the baseball?

A

11500 N

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11
Q

A 57g tennis ball is thrown upward and struck just as it comes to rest at the top of its motion. If the racket exerts an average force of 420N on the ball, find the speed of the ball after the collision if they are in contact for 4.5ms

A

39 m/s

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12
Q

A truck’s initial momentum is 5.8x10^4 kg m/s [W]. An average force of 4.8x10^3 N [W] increases the truck’s momentum for the next 3.5s. What is the impulse and final momentum of the truck?

A

J=1.7x10^4 Ns

p=7.5x10^4 Ns

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13
Q

Two football players charge toward each other to make a tackle. The first player with a mass of 65kg, is moving at 8.2m/s [L] while the second player with a mass of 59kg, is moving at 7.4m/s [R]. If they collide inelastically, what is the final velocity?

A

0.78 m/s

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14
Q

A vacationer of mass 75kg is standing on a stationary raft of mass 55kg. The vacationer then walks toward one end of the raft at a speed of 2.3m/s [W] relative to the water. What is the velocity of the raft?

A

(3.1m/s [E])

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15
Q

A 34kg kid is riding down a level street on his 2.5kg skateboard. If he is travelling at 3.8m/s and then jumps off, and come to rest, what is the final velocity of the skateboard?

A

(55.5m/s)

16
Q

A 0.045kg golf ball is hit with a driver. The head of the driver has a mass of 0.15kg and travels at 56m/s before the collision. The ball has a speed of 67m/s as it leaves the club face. What is the speed of the driver after the collision?

A

36 m/s

17
Q

An object of mass m has an elastic collision with another object initially at rest and continues to move in its original direction but with one-third of its original speed. After the collision, the second object is moving at double the initial velocity of the first mass. What is the mass of the second object in terms of m?

A

m2=m1/3

18
Q

Inelastic Collision

A

2 objects collide and stick together

19
Q

Elastic Collision

A

2 objects collide and bounce off each other

20
Q

Explosion Collision

A

One object breaks apart

21
Q

The ball launcher in a pinball machine has a spring that has a force constant of 1.20 N/cm. The surface on which the ball moves is inclined 10 degrees. If the spring is originally compressed 5cm, find the launching speed of the 100 g ball when the plunger is released. Friction is negligible

A

1.68 m/s

22
Q

A 5g bullet is shot at a block of mass 1.5kg that is connected to a spring. The bullet has an initial speed of 400 m/s and imbeds itself fully in the block which is a frictionless surface. If the spring has constant of 900 N/m, find the distance it compresses.

A

5.4cm

23
Q

An 80.0kg astronaut is working on a satellite which is drifting through space at a constant velocity. The astronaut, wishing to get a better view of the Universe, pushes off the satellite, mass 325kg, when 120s later he is 30m behind the satellite. Without a thruster, the only way for the astronaut to get back is to throw his 5kg wrench directly away from the satellite. If he throws the wrench at a speed of 35m/s, how long does it take the astronaut to return to the satellite?

A

16s

24
Q

A 2kg wooden block is on a level board and held against a spring of force constant 150 N/m, which has been compressed 15cm. The block is released from the rest and propelled horizontally across the board. The coefficient of friction between the block and the board is 0.25 - Assume that friction between the block and is negligible until the point where the block losses contact with the spring. Determine the total distance travelled by the block.

A

34.5cm

25
Q

A missile has a mass of M and is moving with a velocity of 255 m/s when it explodes in midair, breaking into two masses M/4 and 3M/4. If the less massive piece flies off at angle of 60°, with respect to the original direction of motion, with an initial speed of 450 m/s, what is the initial velocity of the other piece?

A

295 m/s [S 64° E]

26
Q

A football player kicks a field goal. The ball is travelling through the air, and hits the bottom of the goal post and bounces straight back. If the initial velocity of the ball is 17.8 m/s, and the collision occurs over a time of 0.689s, how much force did it take to bring the 785g football to a stop?

A

-20.3 N

Physics (4 decks)

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