Question

A bullet of 10 g strikes a sand bag at a speed of 10 m/s and gets embedded after travelling 5 cm.
Calculate. (i) The resistive force exerted by the sand on the bullet. (ii) The time taken by the
bullet to come to rest.
(Ans: -10% N, 104 s)​

Answer 1

Answer:F = -10N

t = 0.01s

Explanation:

We know v²=u²-2as

Here v = 0

u = 10m/s

s = 5cm = 0.05m

So, 0²=10²-2a×5/100=a/10

or a = 1000

Mass of bullet = 10g = 0.01kg

The force will be negative as it is applied opposite to the direction of motion

So the force = -0.01×1000N = -10N

Now we also know v=u-at

Here v = 0, u =10m/s, a =  1000m/s²

So t = u/a = 0.01s

I think your second answer is wrong. Think it practically, a bullet can't  move through sand bag for 104 s.

Hope this will help you.