Q. A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time, the particle goes up is
1) –0.5 J
2) –1.25 J
3) 1.25 J
4) 0.5 J
Answer:
2) –1.25 J
Solution:
Mass = 100 g
Speed, u = 5 m/s
Work done by the force of gravity is the kinetic energy while moving up
Wg = (1/2)mvf2 – (1/2)mvi2
= 0 – (1/2) x (0.1 kg) x 25
= -1.25 J