Chapter 6

The momentum of an object is not dependent on which of the following quantities? Inertia Mass Velocity Acceleration

Acceleration

Think about an object whose momentum is originally 5 kg*m/s in the positive x-direction. Later, the object's momentum is 5 kg *m/s in the negative x-direction. How would you describe the object's motion?

At some point the object experiences a force.

Two equal mass objects are moving toward each other with equal speeds. If they collide completely inelastically, what will happen to the objects?

Each object comes to rest.

True or False: To determine the total momentum of a system of objects, we simply ad the magnitudes of the momenta.

False

Two masses collide inelastically. Neither kinetic energy nor momentum is conserved. True or False?

False.

You watch two objects collide elastically. Object A is initially moving towards object B, which is at rest. After the collision, object A is at rest and object B is moving. What must be true of the masses of the objects?

Objects A and B must have the same mass.

Imagine you are at the middle of the surface of a frozen lake that is frictionless. What would get you to the edge in the shortest amount of time?

Pick a direction you'd like to move and then throw your boots as hard as possible in the opposite direction.

If the acceleration of the center of mass of a system of particles is zero, what happens to the net external force and the accelerations?

The net external force on the system must be zero, but the individual particles may have non-zero accelerations.

An electron and a neutron collide elastically. The electron is initially at rest. How would you describe the motion of the electron and neutron?

The neutron continues its motion with approximately the same speed and the electron moves in the same direction with a larger speed.

Two equal mass objects collide inelastically. One of the objects is initially at rest. What would you predict about the speeds of the objects?

The speed of the final object is smaller than the speed of the initially moving object.

Two cars are approaching an intersection; one car is traveling north, the other is moving south. The cars have identical masses and speeds. How would you describe the momentum of this system?

The system momentum is zero.

What happens to the kinetic energy in an elastic collision?

The total value of the system's kinetic energy does not change.

The center of mass location of an arbitrary object is not necessarily within the boundaries of the object. True or false?

True

The center of mass of a system of particles has a constant velocity if the external forces acting on the particles of the system sum to zero. True or False?

True

A firecracker sits at rest on the ground. When it explodes, it is ripped into multiple pieces that scatter in all directions. True or False: The momentum of the firecracker system after the explosion is zero.

True.

Two masses collide elastically. Both kinetic energy and momentum are conserved. True or False?

True.

Imagine a barbell that has two different masses connected by a thin bar; one of the masses is twice as large as the other. Where would you expect the location of the center of mass?

You would expect the center of mass to be closer to the more massive end.

For an object with a fixed mass, doubling its momentum

increases its kinetic energy by a factor of 4.

The conservation of momentum

is guaranteed if the net force on a system is zero.

Which of the following units are used for an impulse? kg* m/s N/s N*kg/s kg/m

kg*m/s

Equal forces are applied to objects A and B, but object A is more massive than object B. If the forces act on A and B for equal amounts of time, what happens to the changes in momentum?

objects A and B experience equal changes in momentum

Complete the following statement: The center of mass is

the point within an object that moves as if all of the object's mass were located there.

The momentum of an object depends upon

the product of its mass and velocity

Imagine throwing an object horizontally from the top of a building. If you ignore air resistance, and positive is up, what happens to the x-component and the y-component?

the x-component of the momentum will remain constant, but the y-component will become more negative.

An object is moving without accelerating. You expect the momentum

to remain constant.

A bullet sits in a gun. The mass of the bullet is much smaller than the mass of the gun. Upon firing the gun, what would you expect of the motion of the gun and the bullet?

you would expect the bullet and gun to move in opposite directions, with the bullet having the larger speed.