Question

Can you explain how it's -50J?

Answer 1

m of bullet=0.01 kg
u of bullet=100 m/s
v of bullet=0
s covers by bullet= 0.1m
Using third equation of motion,
v^2 - u^2 = 2as
(0)^2-(100)^2=2×a×0.1
a=-100×100/2×0.1
Therefore, a=-50000m/s
Then,
F=ma
F=0.01×-50000
F=-500 N
Now,
W=FS
W=-500×0.1
therefore, W=-50 j
Hope it helps you.