Force & Torque: Acceleration, Power & Angular Velocity

[Mohammed Ayaz Quadri]

How can Force, sometimes instead of accelerating moves an object with a uniform motion. And how Power equals force into speed if force should accelerate. What does torque do, accelerate angularly or move object with unform angular velocity. How Power equals Torque into Angular Velocity if torque is due to a force with should constantly increase magnitude of velocity of object.

 

[CWatters]

How can Force, sometimes instead of accelerating moves an object with a uniform motion.

The relevant equation is

Force = mass * acceleration ... (1)

Where Force is the net force acting on the object. So you only get get acceleration if there is a net force acting on the object. So for example an aircraft moves at a constant velocity when thrust = drag. In that case there is no net force acting on the aircraft in the horizontal direction.

And how Power equals force into speed if force should accelerate.

Work = force * displacement
Power = Work/time
So...
Power = force * displacement/time

Displacement/time = velocity
So...
Power = force * velocity

What does torque do, accelerate angularly or move object with unform angular velocity.

The relevant equation is

Torque = moment of inertia * angular acceleration...(2)

Where Torque is the net torque acting on the object. Compate equation 2 with 1 above.

How Power equals Torque into Angular Velocity if torque is due to a force with should constantly increase magnitude of velocity of object.

Work = torque * angular displacement
Power = work/time
So...
Power = torque * angular displacement/time

Angular displacement/time = angular velocity
So...
Power = torque * angular velocity

 

[CWatters]

Note that the equation for calculating acceleration use the NET force or torque. The equations for calculating the power use the force or torque provided by the engine. Do you see the difference?