# Kinetic Energy when the Force is Perpendicular to Velocity

1. Jul 8, 2016

1. The problem statement, all variables and given/known data
Given, force of constant magnitude, which is always perpendicular to the velocity of the particle & the motion takes place in a plane. What happens to its kinetic energy? Explain.
2. Relevant equations
Work energy theorem
3. The attempt at a solution
According to work energy theorem, the work done turns out to be zero. This implies that the change in kinetic energy is zero i.e. the kinetic energy is constant.

2. Jul 8, 2016

### Clever Penguin

Yes, this is completely correct. The change in kinetic energy is zero.

3. Jul 8, 2016

But there is a problem. Can we answer this question in other words where this work energy theorem is not used?

4. Jul 8, 2016

### cnh1995

Since force is perpendicular to the velocity, it has no component along the direction of the velocity vector. This means the force can't change the magnitude of the velocity. Hence, it remains constant.

5. Jul 8, 2016