Two cars are initially moving with speeds va and vb. the cars are decelerated at the same rate until they come to a stop. if it takes car a four times as far to stop as car b, then how do their initial speeds compare?

Explanation:

As we know that the speed of car A and car B is given by

&

now we know that both cars are decelerated by same deceleration and stopped finally

so the distance moved by the car is given by the equations

similarly we have

now we know that

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.