Velocity changes when force applied perpendicular

[asmnath]

Homework Statement

velocity changes when force applied perpendicular

i can't understand a simple question.
can u help me
what i know is that speed in short its magnitude does not change when force is applied perpendicular.its direction only changes so does the velocity.
what i don't understand is how do this velocity changes direction when we apply force perpendicular.can u tell me any proof or in detail about how they are related.
also can u tell me in uniform circular motion how velocity changes and what exactly is centripetal force and centrifugal force.

please tell me in detail like some proof u see
when they are pependiulcar we calculate resultant and still it doesn't change anything like that

Homework Equations

The Attempt at a Solution

 

[CWatters]

what i know is that speed in short its magnitude does not change when force is applied perpendicular

That's not quite correct. The component in the original direction won't change but the speed in the new direction can change.

Consider a man cycling north at 5 mph when he is hit by a car traveling east at 50mph. He bounces off the car goes flying through the air. The man will end up traveling in a new direction (slightly north of east) and considerably faster than 5mph. However the northerly component of his new velocity will still be 5mph (assuming no friction between him and the car during the collision).