Arock is thrown upwards at 15 m/s and reaches a maximum height before
it falls back to earth. what is its velocity immediately after it reaches this
maximum height?
a) 0 m/s
b) o m/s downwards
c) 15 m/s
d 9.8 m/s2

Answer:

The velocity of the rock at the maximum height that thrown upwards at 15 m/s is 0 m/s

Explanation:

When an object is thrown upwards, it will fall back to the ground due to the earth's gravity. All objects closer to the earth's surface falls down with a constant acceleration of about 9.8m m s^{-2}. This is known as  the acceleration due to gravity and is usually represented  by the letter g.

An object that is thrown vertically upwards decelerates down due to the earth's gravity. Its speed gets decreased until it reaches the maximum height . At the maximum height velocity becomes zero. Then it is accelerated uniformly downwards under gravity.  

the device is called “ rocket engine”