Question

A ball of mass 100 gm is projected upwards with velocity 10 m/s. It returns back with 6 m/s. Find work done by air resistance.

Answer 1

W net =W mg +W air = 1 2 m(v f ^ 2 -v i ^ 2 )

Rightarrow0+W air = 1 2 *0.1[(6)^ 2 -(10)^ 2 ]=- - 3.2

From work energy thergy theorem,

Answer 2

W_net=W_mg + W_{air resistance}

According to Work-Energy theorem,

W_net = change in K.E.

 So, W_mg = 0 and W_air = 1/2m(v_f ² - v_i ² )

  =1/2×0.1(6² - 10² ) = -3.2 J.