1. a. Two identical steel balls, each of mass 2.8 kg, are suspended from strings

Question

1. a. Two identical steel balls, each of mass 2.8 kg, are suspended from strings of length 30 cm so that they touch when in their equilibrium position. We pull one of the balls back until its string makes an angle theta = 42o 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?

2. A 12.0-kg shell is fired from a gun with a muzzle velocity 90.0 m/s at 36.0o 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?

Explanation / Answer

2) at highest point speed is only horizontal and = 90cos36 = 72.81 m/s

now m x 72.81 = m/2 x 0 + m/2 x v

v = 145.62 m/s

1) a) as both mass are equal than on collision both will exchange the velocities in elastic collision, so 2nd mass will attain the same height as the first was initially.

h = 30(1 - cos42) = 7.7056 cm

b) as mass will stuck so velocity will be half as before collision on coservig momentum, also height is proportional to the square of velocity.

so height will be 0.25 times the initial = 7.7056/4 = 1.9264 cm

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