SparkNotes: Review of Linear Momentum: Test

1. The center of mass is defined as

(A) The position of the most massive particle in a given system

(B) The point at which a net external force applied to all the mass of the system at that point would produce the same acceleration of the system as if it were applied to each particle individually

(C) The average position of each particle

(D) The point equidistant from all particles in a system

2. The equation for the center of mass of two particles is

(A) x_cm =

(B) x_cm = m₁x₁ + m₂x₂

(C) x_cm =

(D) x_cm =

3. A particle of mass 1 kg is located at (0,0) and a particle of mass 2 kg is located at (3,0). What is the location of the center of mass of this system?

(A) (0,0)

(B) (1,0)

(C) (1.5,0)

(D) (2,0)

4. The net external force on a system of particles is zero. What is the velocity of the center of mass of the system?

(A) 0

(B) Constant

(C) Constantly increasing

(D) Constantly decreasing

5. The net external force on a system of particles is zero. What is the velocity of each particle in the system?

(A) 0

(B) Constant

(C) Constantly increasing

(D) Not enough information

6. Four particles of equal mass are at points (0,0), (2,0), (2,2) and (0,2). Where is the center of mass of the system?

(A) (1,0)

(B) (1,1)

(C) (2,0)

(D) (2,2)

7. Where is the center of mass of a single particle?

(A) The point halfway between the particle and the origin

(B) The origin

(C) The position of the particle

(D) Undefined

8. A net force of 8 N is applied to a system containing four masses, each of 1kg. What is the resultant acceleration of the center of mass of the system?

(A) 2 m/s

(B) 8 m/s

(C) 12 m/s

(D) 32 m/s

9. What is the definition of impulse?

(A) Force per unit time

(B) Force per unit distance

(C) Force over a distance

(D) Force over a time

10. What is the equation for impulse?

(A) F/t

(B)

(C) Ft

(D) Fx

11. A bat exerts a force on a ball of 100 N for a period of .1 seconds. What is the impulse provided by the bat?

(A) 100

(B) 10

(C) 1000

(D) 10

12. What is the definition of momentum?

(A) ma

(B) mv²

(C)

mv²

(D) mv

13. A net impulse on an object causes

(A) A change in its kinetic energy

(B) A change in its speed

(C) A change in its momentum

(D) A change in its mass

14. What is the relation between force and momentum?

(A) F = Δp

(B) F =

(C) F = pt

(D) F = px

15. A ball of mass 2 kg bounces against a wall with a velocity of 6 m/s and rebounds with the same velocity. What is the impulse provided by the wall?

(A) 12

(B) 24

(C) 3

(D) 8

16. What are the units of momentum, in terms of fundamental units?

(A) N-s

(B) kg-m/s

(C) J/s

(D) kg-m

17. What are the units of impulse, in terms of fundamental units?

(A) N-s

(B) kg-m/s

(C) J/s

(D) kg-m

18. Both momentum and kinetic energy are dependent on what variable?

(A) Acceleration

(B) Position

(C) Work

(D) Velocity

19. A 4 kg mass has a momentum of 2 N-s. What is the kinetic energy of the mass?

(A) 1 J

(B) 2 J

(C) 8 J

(D) Cannot be determined

20. What is the mass of an object that moves 10 meters in 2 seconds, and has a momentum of 10 N-s?

(A) 1 kg

(B) 2 kg

(C) 5 kg

(D) 10 kg

21. What is the definition of the momentum of a system of particles?

(A) P = M(v₁ + v₂ + ^... + v_n)

(B) P = Mv₁v₂^...v_n

(C) P = Mv_cm

(D) P = Ma_cm

22. The total momentum of a system of particles is conserved only if

(A) There are no interactions between the particles

(B) The velocity of the center of mass of the system is constant

(C) The velocity of the center of mass of the system is zero

(D) The system conserves energy

23. What is the linear momentum of a system of two particles with equal mass m travelling in opposite directions with speed v?

(A) 0

(B) 2mv

(C) mv

(D) mv/2

24. A cannon of mass 100 kg fires a shell of mass 10 kg at a speed of 100 m/s. With what speed does the cannon recoil?

(A) 0

(B) 1 m/s

(C) 100 m/s

(D) 10 m/s

25. A missile explodes in midair. What statement can be made about the motion of the system after the explosion?

(A) Each fragment from the explosion falls directly to the ground.

(B) The center of mass of the system continues in the same path as the missile before the explosion.

(C) The center of mass of the system moves with constant velocity.

(D) The total linear momentum of each piece of the explosion is zero.

26. A mass of 2 kg moves in the positive x direction with a speed of 2 m/s. A mass of 1 kg moves in the negative x direction with a speed of 3 m/s. What is the total momentum of this system?

(A) 1 kg-m/s

(B) 7 kg-m/s

(C) 8 kg-m/s

(D) 5 kg-m/s

27. A mass of 2 kg moves in the positive x direction with a speed of 2 m/s. A mass of 1 kg moves in the negative x direction with a speed of 3 m/s. What is the velocity of the center of mass of this system?

(A) 1 m/s

(B) 2 m/s

(C) .33 m/s

(D) .66 m/s

28. If the total linear momentum of a system is zero, it can be deduced that

(A) The center of mass of the system has no velocity

(B) No particles in the system are moving

(C) No net external force is acting upon the system

(D) There are no forces between particles in the system

29. In which of the following situations is momentum NOT conserved?

(A) Two objects colliding

(B) A group of skydivers falling to the earth

(C) An object moving horizontally with constant speed

(D) A rocket in deep space firing its engines

30. Two cars of equal mass collide head on and both come to a stop. What can be said about the cars before the crash?

(A) The velocity of each car was relatively low

(B) They were moving in the same direction

(C) They put on their brakes

(D) They were moving with equal speeds in opposite directions

31. A baseball of mass 1 kg is hit by a bat, changing its velocity from 50 m/s in one direction to 50 m/s in the opposite direction. What is the impulse provided by the bat?

(A) 100 N-m

(B) 50 N-m

(C) 25 N-m

(D) 10 N-m

32. A baseball of mass 1 kg is hit by a bat, changing its velocity from 50 m/s in one direction to 50 m/s in the opposite direction. The bat is in contact with the ball for .1 seconds. What is the average force provided by the bat over this time?

(A) 100 N

(B) 50 N

(C) 500 N

(D) 1000 N

33. A net force of 50 N acts on a particle for 1 second. What is the impulse provided by the force?

(A) 100 N-s

(B) 25 N-s

(C) 50 N-s

(D) 150 N-s

34. A net force of 50 N acts on a particle of mass 5 kg for 1 second. What is the change in the velocity of the particle?

(A) 50 m/s

(B) 25 m/s

(C) 5 m/s

(D) 10 m/s

35. Are impulse and momentum vector or scalar quantities?

(A) Impulse is a vector, momentum is a scalar

(B) Impulse is a scalar, momentum is a vector

(C) Both are vectors

(D) Both are scalars

36. What is the definition of an elastic collision?

(A) Momentum is conserved

(B) The velocity of the center of mass of the system does not change

(C) Kinetic energy is conserved

(D) Both particles retain their original velocities

37. What is the definition of a completely inelastic collision?

(A) The two particles stick together

(B) Momentum is not conserved

(C) Kinetic energy is not conserved

(D) Both particles have a final velocity of zero

38. Two particles of the same mass and speed collide head on in an elastic collision. What can be said about the final velocity of each particle?

(A) They are both zero

(B) They are both the same as their initial velocities

(C) The have the same magnitude and opposite direction as their initial velocities

(D) Not enough information

39. Which of the following problems, given initial conditions of mass and velocity of each particle, is NOT solvable?

(A) A head on elastic collision

(B) A two dimensional elastic collision

(C) A head on completely inelastic collision

(D) A two dimensional completely inelastic collision

40. A particle of mass 1 kg moving at a velocity of 50 m/s hits a particle of mass 1 kg, at rest in an elastic collision. What is the final velocity of the second particle?

(A) 0

(B) 25 m/s

(C) 100 m/s

(D) 50 m/s

41. A particle of mass 1 kg moving at a velocity of 50 m/s hits a particle of mass 1 kg, at rest in a completely inelastic collision. What is the final velocity of the second particle?

(A) 0

(B) 25 m/s

(C) 100 m/s

(D) 50 m/s

42. A particle of mass 1 kg moving along the x axis collides with a particle of mass 1 kg moving along the y axis with the same speed in a completely inelastic collision. What is the angle each particle makes with the x axis?

(A) 45^o

(B) 90^o

(C) 180^o

(D) 0^o

43. How many equations can we use to solve a one dimensional elastic collision problem?

(A) 1

(B) 2

(C) 3

(D) 4

44. How many equations can we use to solve a one dimensional completely inelastic collision problem?

(A) 1

(B) 2

(C) 3

(D) 4

45. How many equations can we use to solve a two dimensional elastic collision problem?

(A) 1

(B) 2

(C) 3

(D) 4

46. How many equations can we use to solve a two dimensional completely inelastic collision problem?

(A) 1

(B) 2

(C) 3

(D) 4

47. In EVERY collision problem, what is conserved?

(A) Kinetic energy

(B) Total mechanical energy

(C) The sum of the velocities of the particles involved

(D) Momentum

48. A particle at rest explodes into two pieces. What can be said about the motion of each piece?

(A) They both are stationary after the explosion

(B) They must move in opposite directions

(C) They must have equal masses

(D) Nothing can be said without knowing the nature of the explosion

49. The collision of two pool balls is approximately what kind of collision?

(A) Inelastic

(B) Elastic

(C) Completely inelastic

(D) Depends on the nature of the collision

50. In any isolated system (with no external forces acting) which of the following is NOT conserved?

(A) Momentum

(B) Energy

(C) Kinetic energy

(D) The velocity of the center of mass of the system

Review of Oscillations

Test