Physics 2414
Midterm #3 – Spring 2005
Version A
Multiple Choice (6 pts each)
1)Two pucks are pushed along a frictionless air hockey board with a force F. Puck A has three times the mass of puck B. Each puck is pushed for the same time t. Consider the motion of the pucks after time t. Which of the following statements is true?
A)The momentum of the pucks is not equal but the kinetic energy of the pucks is equal.
B)The momentum and kinetic energy of the pucks is equal
C)The momentum of the pucks is equal but the kinetic energy is not equal
D)The distance traveled is the same
E)Neither the momentum nor the kinetic energy is the same.
2)You are on a cart initially at rest on a track with no friction. You throw balls at a partition that is rigidly mounted on the cart. If the balls bounce straight back as shown, is the cart put into motion?
A)Yes, it moves to the left
B)Yes, it moves to the right
C)No, it remains in place
D)Yes, it can move either left or right
depending on how hard the balls are thrown.
E)Not enough information to determine.
3)Two squares of the same mass are shown. Where is the location of the center of mass?
A)Xcm=2 cm; Ycm=2 cm
B)Xcm=5 cm; Ycm=3 cm
C)Xcm=5/2 cm; Ycm=2/3 cm
D)Xcm=7/2 cm; Ycm=3/2 cm
E)Xcm=3/2 cm; Ycm=3/2 cm
4) A skier of mass 100 kg starts from a hill 10 m high and skies to the bottom of the hill. When the skier reaches the bottom of the hill he picks up a box of mass 20 kg. What is the speed of the skier immediately after he picks up the box?
A)14.00 m/s
B)11.67 m/s
C) 9.45 m/s
D)163.33 m/s
E)70.00 m/s
5)If the momentum of a ball is doubled, then the kinetic energy is,
A) 0.50 times larger
B) 0.71 times larger
C) 2.00 times larger
D) 3.00 times larger
E) 4.00 times larger
6) In any isolated collision,
A) Total momentum is not conserved.
B) Total kinetic energy is conserved.
C) Total momentum is conserved.
D) Total momentum is not conserved but total kinetic energy is conserved.
E) Total momentum and total kinetic energy are conserved.
7) A 90 kg person is sitting in a boat at rest with a mass of 100 kg. In the boat is a stone with a mass of 5.0 kg. The person throws the stone at 4.0 m/s horizontally in the NORTH direction. The velocity of the person and the boat after the throwing of the stone is,
A) 2.00 m/s SOUTH
B) 1.21 m/s SOUTH
C) 1.21 m/s NORTH
D) 0.11 m/s SOUTH
E) 0.11 m/s NORTH
8) A 4.0 kg object is moving at 5.0 m/s SOUTH. It strikes a 3.0 kg object that is moving WEST at 2.0 m/s. The objects have a completely inelastic (stick together) collision. The kinetic energy lost in the collision is,
A) 25 J
B) 18.4 J
C) 10.5 J
D) 8.33 J
E) 2.61 J
9) An 1800 kg car moving at 40 m/s hits an initially uncompressed spring with a spring constant of 2.0 x 10 N/m. The maximum compression of the spring is,
A) 1.44 m
B) 0.6 m
C) 0.8 m
D) 1.0 m
E) 1.2 m
10) A skier of mass = 80kg starts from rest on the top of a hill. She skies down the hill and a frictional force of 300 N opposes her motion. Just when she reaches the bottom of the hill she comes to a stop. What is the angle of the hill with respect to the horizontal?
A)22.5 degrees
B)30.0 degrees
C)15.0 degrees
D)45.0 degrees
E)It depends on the height of the hill
11)A ball of mass 2 kg is dropped from a height of 5 meters and rebounds back to a height of 5 meters. The ball hits the floor for a time 0.2 seconds. What is the average force on the ball from the floor?
A) 99 N
B)39.6 N
C)9.9 N
D)198 N
E)20.3 N
12) A 20 N force is applied at an angle of 40 degrees above the horizontal to a 4.0 kg box. The box moves a horizontal distance of 4.0 meters. The work done by the 20 N force is,
A) 75.0 J
B) 61.3 J
C) 50.1 J
D) 46.3 J
E) 40.5 J
13) A 120 kg mass is blown apart into a 80 kg piece and a 40 kg piece. After the blast, the two masses are moving apart with a relative velocity of 60 m/s. The velocity of the 80 kg mass is,
A) 59 m/s
B) 51 m/s
C) 34 m/s
D) 20 m/s
E) 14 m/s
14) A basketball bounces on the floor as shown. Which statement below is true?
A) the momentum of the basketball parallel to the floor is conserved.
B) the momentum of the basketball perpendicular to the floor is conserved.
C) the total momentum of the basketball is conserved.
D) none of the momentum components of the basketball conserved.
E) it depends on the mass of the ball.
15) A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the collision force is correct?
- The small car experiences the greater average force.
- The truck experiences the greater average force.
- The small car and the truck experience the same average force.
- It is impossible to tell since the masses and velocities are not given.
- none of the above.
16) A woman stands on the edge of a cliff. She throws a stone vertically downward with an initial speed of 15 m/s. The instant before the stone hits the ground below, it has 150 J of kinetic energy. If she were to throw the stone horizontally outward from the cliff with the same initial speed of 15 m/s, how much kinetic energy would it have just before it hits the ground?
- 50 J
- 150 J
- 450 J
- 900 J
- Not enough information was given to answer the question