Question

A particle is performing circular motion with decreasing speed.If force on particle is f and velocity at instant is V then
1)F.V=0
2)F.V greater than 0
3)F.V less than 0
4)F.V greater than or equal to 0

Answer 1

Answer:

Option (3) F.V less than 0

Explanation:

There will be two forces acting when the circular motion is occurring with a decreasing speed.

The centripetal acceleration will be perpendicular to the velocity, therefore, its dot product will with the velocity vector will be zero

But  a force due to retardation will be acting opposite to the velocity vector, the angle between them will be 180° and since cos180° = -1, therefore, the dot product will be negative

hence the overall dot product will be negative.

Hope this helps.