Exam 9: Center of Mass and Linear Momentum

Two 4.0-kg blocks are tied together with a compressed spring between them.They are thrown from the ground with an initial velocity of 35 m/s, 45 $\degree$ above the horizontal.At the highest point of the trajectory they become untied and spring apart.About how far below the highest point is the center of mass of the two-block system 2.0 s later, before either fragment has hit the ground?

A 5-kg object can move along the x axis.It is subjected to a force in the positive x direction; a graph of F as a function of time t is shown below.Over the time the force is applied the change in the velocity of the object is:

The physical quantity "impulse" has the same dimensions as that of:

Two identical carts travel at 1 m/s on a common surface.They collide head-on and are reported to rebound, each with a speed of 2 m/s.Then:

A shell is launched from a cannon and explodes mid-air.Which of the following is correct after the explosion?

For a completely inelastic two-body collision the kinetic energy retained by the objects is the same as:

The momentum of an object at a given instant is in the same direction as its:

The momentum of an object at a given instant is independent of its:

The force on a particle is given by F(t)= 0.71 t + 1.2 t², in N.If the force acts from t = 0 to t = 2.0 s, the total impulse is:

A ball hits a wall and rebounds with the same speed, as diagrammed below.The changes in the components of the momentum of the ball are:

Block A, with a mass of 2.0 kg, moves along the x axis with a velocity of 5.0 m/s in the positive x direction.It suffers an elastic collision with block B, initially at rest, and the blocks leave the collision along the x axis.If B is much more massive than A, the velocity of A after the collision is:

A particle moves along the x axis.Its momentum is graphed below as a function of time.Rank the numbered regions according to the magnitude of the force acting on the particle, least to greatest.

A student's life was saved in an automobile accident because an airbag expanded in front of his head.If the car had not been equipped with an airbag, the windshield would have stopped the motion of his head in a much shorter time.Compared to the windshield, the airbag:

Block A, with a mass of 4.0 kg, is moving with a speed of 2.0 m/s while block B, with a mass of 8.0 kg, is moving in the opposite direction with a speed of 3.0 m/s.The center of mass of the two-block system is moving with the velocity of:

A man sits in the back of a canoe in still water.He then moves to the front of the canoe and sits there.Afterwards the canoe:

Two bodies, A and B, have equal kinetic energies.The mass of A is nine times that of B.The ratio of the momentum of A to that of B is:

A uniform narrow bar, resting on frictionless ice, is given a transverse horizontal impulse at one end as shown.The center of mass of the bar COM will then:

A 640-N hunter gets a rope around a 3200-N polar bear.They are stationary, 20 m apart, on frictionless level ice.When the hunter pulls the polar bear to him, the polar bear will move:

At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s.They move along nearby lines and pass without colliding.At the end of 2.0 s the velocity of the center of mass of the two-ball system is:

The x and y coordinates in meters of the center of mass of the three-particle system shown below are: