17. A car is accelerated at 4.0 m/s2 from rest. How long does it take the car to reach a speed of 28 meters per second?

t = 7 seconds

Explanation:

Given that,

The acceleration of a car, a = 4 m/s²

The initial velocity of the car, u = 0

Final velocity of the car, v = 28 m/s

We need to find how much time the car to reach a speed of 28 m/s. Using the definition of the acceleration of a car. It is given by :

So, it will take 7 seconds to reach a speed of 28 m/s.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.