9. An object moving at a constant velocity accelerates at a constant rate of 20 m/s for a distance of 100 m. At the end of the acceleration the object has a velocity of 80 m/s. What was its velocity
before accelerating?

I believe the answer is roughly 49m/s

Explanation:

List all given variables:

Accel=20m/s^2

Dist=100m

Final velocity=80m/s

Initial velocity=?

Using the equation i=sqrt(f^2-2a*d) where i =initial velocity, f=final velocity, a=acceleration, and d=distance, we can plug in the known values and solve for initial velocity

i=sqrt(80^2-2*20*100)

i=sqrt(6400-4000)

i=sqrt(2400)

i=48.99, rounded up to 49m/s as the initial velocity

This is my speculation about this answer would appreciate if anyone can confirm this.

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.