Astring that passes over a pulley has a 300 kg mass attached to one end and a 450 kg mass attached to the other end. the pulley, which is a disk of radius 10 cm, has friction in its axle. what is the magnitude of the frictional torque that must be exerted by the axle if the system is to be in static equilibrium?

147 N-m

Explanation:

Given

mass of first Pulley

mass of second Pulley

radius of Pulley

If the system is in equilibrium then tension in the side mass is

Tension in side block

Net torque is

therefore Frictional Force must apply a force of 147 N-m in order to system remains in equilibrium

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.