# PHYSICS

PHYSICS[1pt] A 50-kg shell is fired from a gun with a muzzle velocity 75 m/s at 74^{o}above the horizontal. At the top of the trajectory, the shell explodes into two fragments of equal mass. One fragment, whose speed immediately after the explosion is zero, falls vertically. What is the horizontal speed of the other fragment?

**Answer:**

2.[1pt]

Two identical steel balls, each of mass 2.9 kg, are suspended from strings of
length 29 cm so that they touch when in their equilibrium position. We pull one
of the balls back until its string makes an angle theta = 31^{o}with
the vertical and let it go. It collides elastically with the other ball. How
high will the other ball rise above its starting point?

**Answer:**

3.[1pt]

Suppose that instead of steel balls we use putty balls. They will collide
inelastically and remain stuck together after the collision. How high will the
balls rise after the collision?

**Answer:**

4. [1pt]

A bullet of mass m= 3.40×10^{-2}kg is fired along an incline and imbeds
itself quickly into a block of wood of mass M= 1.45kg. The block and bullet
then slide up the incline, assumed frictionless, and rise a height H= 1.25m
before stopping. Calculate the speed of the bullet just before it hits the
wood.

**Answer:**

5.[1pt]

A car, mass m_{1} is moving to the right on a frictionless air
track. It collides with a second car, mass m_{2}, which is initially at
rest. Which of the following statements are true? (If A and E are true, and the
others are not, enter TFFFT).

A) If car 1 is much lighter than m2, and the collision is perfectly elastic,
car 1 will continue heading to the right with nearly its original speed after
the collision.

B) If car 1 sticks to car 2, the car1-car2 system must move to the right after
the collision.

C) If car 1 sticks to car 2, the final total kinetic energy of the car1-car2
system is less than the initial total kinetic energy of the two cars.

D) If the collision is elastic, car 1 must always come to a stop after the
collision.

E) Suppose (for this statement only) that car 2 was NOT initially at rest, but
was instead heading towards car 1 with equal (but opposite) momentum before the
collision. After the collision, the cars must both be at rest.

**Answer:**

6.[1pt]

A ball of mass 4.0 g with a speed of 29.2 m/s strikes a wall at an angle 28.0^{o} and
then rebounds with the same speed and angle. It is in contact with the wall for
41.0 ms. What is the magnitude of the impulse associated with the collision
force?