Three blocks are placed in contact on a horizontal frictionless surface. a constant force of magnitude f is applied to the box of mass m. there is friction between the surfaces of blocks 2m and 3m (μs = 0.26, μk = 0.15) so the three blocks accelerated together to the right.

what is the acceleration of the blocks? (you may assume block 3m does not slide or fall off block 2m.)

what is the maximum force f that can be applied, before the 3m block slides off?

Part a)

Part b)

Explanation:

Part a)

Applied force on the block system is given as

total mass of the system is given as

now acceleration of the system is given as

Part b)

When 3M mass block just start sliding then the force of friction on it will reach to its maximum value

now the acceleration of the block is given as

now we have

3.2x10^7

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.