4.1 Define the term impulse in words - NSC Physical Sciences - Question 4 - 2017 - Paper 1

To calculate the momentum (p) of each bullet, we use the formula:

$p = mv$

Where:

• m = mass of the bullet = 0.03 kg
• v = velocity of the bullet = 700 m/s

Substituting the values:

$p = 0.03 imes 700 = 21 ext{ kg m/s}$

Thus, the magnitude of the momentum of each bullet when it leaves the gun is 21 kg m/s.

To find the net average force exerted on the gun, we can use the relationship between impulse and force:

$F_{avg} = \frac{\Delta p}{\Delta t}$

First, calculate the change in momentum for 220 bullets:

• Total momentum for 220 bullets: $\Delta p = 220 imes 21 = 4620 \text{ kg m/s}$

• The time taken to fire 220 bullets (1 minute = 60 seconds): $\Delta t = 60 ext{ s}$

Now substituting the values into the formula for average force:

$F_{avg} = \frac{4620}{60} = 77 \text{ N}$

Thus, the net average force that each bullet exerts on the gun is 77 N.

The average horizontal force that the mechanical support exerts on the gun is equal and opposite to the net average force exerted by the bullets, which is 77 N in the westward direction.