Question

Bullets of mass 0.03 kg each, hit a plate at the rate of 100 bullets per second with 50m/s velocity, and reflects back with 20m/s. Find average force acting in the plate.

Answer 1

Explanation:

Mass of the body = 0.03 kg .

Final momentum = 100 × 0.03 kg × (-20 m/s)

⇒ - 60 kg m/s

Initial momentum = 100 × 0.03 kg × 50 m/s

⇒ 1 × 3 × 50 kg m/s

⇒ 3 × 50 kg m/s

⇒ 150 kg m/s

Change in momentum = 150 kg m/s - ( -60 kg m/s )

⇒ 210 kg m/s .

Average force acting = change in momentum / time taken

⇒ 210 kg m/s / 1 s

⇒ 210 kg m/s²

⇒ 210 N

Explanation:

Momentum = mass × velocity .

Final momentum = mass × final velocity .

Initial momentum = mass × initial velocity .

The sign of final velocity is taken negative since it is in an opposite direction to the original velocity .

The rate of change of momentum is the difference or the change in the momentum per unit time .