# Strange question in mechanics

What does a force that's perpendicular to velocity do?
it changes its direction while the magnitude (speed) remains the same.

vela
Staff Emeritus
Homework Helper
Right, so the force causes $\vec{v}_\parallel$ to die off, but it changes only the direction of $\vec{v}_\perp$ and not its magnitude.

but who cares about the direction when we want to calculate the kinetic energy ... All we're interested in is the magnitude of $$\vec{v}_{\perp}$$.

But how do I continue from this point? This is my main problem.

ehild
Homework Helper
Determine the initial $$\vec{v}_{\perp}$$ and calculate its magnitude.

ehild

thank you all ... I got it