Question

# A 2.7 kg block is hanging from a string of 7 cm, from the ceiling. The...

A 2.7 kg block is hanging from a string of 7 cm, from the ceiling. The block is struck by a
9 g bullet. After the collision the block and bullet swing up to a height of 20 cm above the initial height.
(a) (5 points) What is the velocity of the block, immediately after being struck by the bullet?
(b) (5 points) What was the impulse delivered to the block, by the bullet? If the collision took 14 ms,
what was the average force applied by the bullet on the block?
(c) (5 points) What was the initial velocity of the bullet before the collision?
(d) (5 points) Aside from the obvious safety reasons, why might shooting a bullet in the air and mea-
suring the maximum height reached by the bullet be a worse method of measuring the speed of a
bullet coming out of a gun.

#### Homework Answers

Answer #1

(a) Now by Conservation of energy

(b) Impulse will be change in momentum. Initial momentum was zero of the block hence

Average force will be

(c) By conservation of momentum

(d) As already calculted, force acted due to the bullet is quite high wich can be harmfull.

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