Often we see on the news people (usually revolutionaries or rebels) celebrating

Question

Often we see on the news people (usually revolutionaries or rebels) celebrating by shooting their rifles into th air. If a person shoots straight up & has an AK-47 model rifle with a muzzle velocity of 715 m/s:

1) How far in altitude does the bullet travel?

2) What is the velocity at the top of th trajectory?

3) What is the speed at the top of the trajectory?

4) How long does it take to reach the top of the trajectory?

5) How long does it take it to fall back to the ground?

6) What is the speed when it reaches the ground?

7) Should you worry if you are next to the shooter?

8) Does the mass of the bullet matter for the answer?

*PLEASE SHOW ALL YOUR WORK

Explanation / Answer

Muzzle Velocity = 715 m/s.

1.) Maximum Height gaind by bullet

Initial energy = final energy

Kinetic Energy = Potential energy

0.5*M*V2 = MgH

0.5 * (715)2 = 9.8 *H

H = 26082.9 meter = 2.6 km

2.) Velocity at top of the trajectory will be Zero. (since it will return after that)

3.)   The speed at the top of the trajectory will also be Zero.

4.) Time taken = u / g = 715 / 9.8 = 72.95 seconds

5.) Time taken to fall back = Time taken to reach top = 72.95 seconds.

6.) Speed will be same the speed with which it was projected i.e 715 m/s

7.) No , I should not worry because the bullet will fall back at shooter.

8.) No, The mass of bullet doesnt matter for all the above calculations.

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