A7.91g bullet is fired into a 1.52-kg ballistic pendulum initially at rest and becomes embedded in it. the pendulum subsequently rises a vertical distance of 6.89 cm. what was the initial speed of the bullet?
a. 0.38 km/s
b. 0.44 km/s
c. 0.50 km/s
d. 0.54 km/s
e. 0.024 km/s

D

Explanation:

By law of conservation of momentum:

momentum before collision = momentum after collision

Initial speed of bullet is unknown whereas initial speed of pendulum will be zero as it was at rest.

Final speed of bullet and pendulum will be equal as bullet is embedded in pendulum and both moves together a vertical distance of 6.89cm.

Using third equation of motion:

where:

Thus by placing values

this speed will be final speed of collision for the calculation of initial speed of bullet.

Putting values:

This 224m/s = 0.224Km/s which is closest to D

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