Question

9. An object is moving with a uniform velocity along a particular direction. Retarding force of 6 Newton is applied in the direction opposite to the direction of displacement . The object stops after a displacement of 24mm. The work done by the retarding force is

Answer 1

According to Newton's second law of motion,

a=−F/m (−ve sign as the force is retarding)

According to third equation of motion,

v

2

=u

2

+2as

Given for v=0,u=u,

Displacement is s

1

⟹s

1

=

2a

u

2

=

2F

u

2

m

................(i)

Given for second scenario,

v=0,u=2u,

Displacement is s

2

⟹s

2

=

2a

(2u)

• 2

=

F

2u

2

m

................(ii)

From (i) and (ii),

s

2

=4s

1