A car starts from rest , then accelerates at 1.20 m/s^2 fo 7.00 s. It hits the brakes, slowing to a stop at a rate of -4.25 m/s^2. What is the total time for the problem? (Unit = s)

8.976 seconds

Explanation:

Initial Velocity (u) = 0

Acceleration (a) = 1.20 m/s^2

Time taken (t) = 7s

Negative acceleration = -4.25 m/s^2

To calculate the total time taken :

Time taken during the first phase of movement = 7 seconds

Final Velocity attained (V) equals :

Using v = u + at

v = 0 + 1.20(7)

v = 0 + 8.4

v = 8.4m/s

Therefore, time taken to bring the car to a stop.

Here final Velocity (v) = 0 ;

Initial Velocity (u) = 8.4m/s

From v = u + at

0 = 8.4 + (-4.25)t

0 = 8.4 - 4.25t

4.25t = 8.4

t = 8.4 / 4.25

t = 1.976 seconds

Therefore, total time taken equals:

7s + 1.976s = 8.976seconds

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.