Q.

An object moving along horizontal x-direction with kinetic energy 10 J is displaced through x=(3i^)m, by the force F=(-2i^+3j^)N. The kinetic energy of the object at the end of the displacement x is:                          [2024]

1 10 J  
2 16 J  
3 4 J  
4 6 J  

Ans.

(3)

Given, F=(-2i^+3j^)N or x=(3i^)m

Initial Kinetic energy, (Ki)=10J

         W=F·x=(-2i^+3j^)·(3i^)=-6J

Using work-energy theorem, W=ΔK.E.

-6=Kf-Ki or -6=Kf-10; Kf=4J