JEE Main Physics question
A force of 20 N is applied on a body of mass 5 kg resting on a horizontal plane. The body gains a kinetic energy of 10 joule after it moves a distance 2 m. The frictional force is
Answer: (B)
Solution
By the work-energy theorem: (F − f)×d = KE ⟹ (20 − f)×2 = 10 ⟹ 40 − 2f = 10 ⟹ f = 15 N.