Question

A bullet of mass 100 g is moving with a speed of 200 ms-1 . What is the k.e of the bullet?

Answer 1

e = 1/2mv^2
therefore, k.e = 1/2×0.1 × 200×200
= 2000 (whatever the unit is)

Answer 2

$kinetic \: energy = \frac{1}{2} m {v}^{2} \\ \\ = \frac{1}{2} \times \frac{100}{1000} \times 200 \times 200 \\ \\ = \frac{1}{2} \times 1/10 \times 40000 \\ \\ = 1/10 \times 20000 \\ \\ = 2000$
as we know 100g = 100/1000 kg
which is inserted in formula
hence 2000 joule