Question

If an object is thrown straight up into the air, what is its acceleration at the top of its flight when its instantaneous velocity is zero?

Answer 1

Acceleration due to gravity `g=9.81ms^-2`

Explanation:

As per Law of Universal Gravitation the force of attraction between two bodies is directly proportional to the product of masses of the two bodies. it is also inversely proportional to the square of the distance between the two. This force of attraction is independent of the direction of motion of the bodies.
`F_G =G (M_1.M_2)/r^2`

Where `G` is the proportionality constant.
It has the value `6.67408 xx 10^-11 m^3 kg^-1 s^-2`

In case one of the bodies is earth the expression reduces to
`F=mg`
As such when an object is thrown straight up into the air there is no change in its acceleration due to gravity at any point of time.