Question

1. A bullet of mass 20g leaves a rifle with a velocity 400 m/s. If the rifle recoils. With

a velocity o 0.75 m/s. Calculate its mass.​

Answer 1

Explanation:

The amount of work done by the resistance of air is 75 J.

Explanation:

Given that,

Mass of bullet = 20 g

Initial speed of bullet = 100 m/s

Final speed = 50 m/s

We need to calculate the work done

Work done = change in kinetic energy

W=\Delta K.EW=ΔK.E

W=\dfrac{1}{2}mv_{i}^2-\dfrac{1}{2}mv_{f}^2W=

2

1

mv

i

2

−

2

1

mv

f

2

Put the value into the formula

W=\dfrac{1}{2}\times20\times10^{-3}\times(100)^2-\dfrac{1}{2}\times20\times10^{-3}\times(50)^2W=

2

1

×20×10

−3

×(100)

2

−

2

1

×20×10

−3

×(50)

2

W=75\ JW=75 J

Hence, The amount of work done by the resistance of air is 75 J.