Gravitation Test - 8

When a body is thrown upwards, the direction of ‘g ‘ is negative that slows down the speed of body. When the body is falling downward, the direction of ‘g’ is downward direction and is positive.

Initial velocity ,u= 20 m/s. final velocity= 0 , g = 10m/s² .
V = u + gt
0= 20 + (-10)t 
-10t = 20
t = 20/10 = 2s. time taken to fall in downward direction = 2s.
Hence total time taken = 2s + 2s = 4s.

The equation of motion for free fall can be used in case of falling of body only due to gravitation of earth without any other force. So, this statement is not true.

Mass of the body (m) = 100 kg, acceleration due to gravity (g) = 9.8 m/s²
Weight (w) = m × g
= 100 × 9.8
=  980 N.

The weight of the body is the measure of force by which earth attracts the body. Acceleration due to gravity is less in case of poles and colour of bears found in these regions are white, called as polar bear.

Acceleration due to gravity (g) on moon is 1/6 th  of the acceleration of gravity (g) on earth. So, weight of body of 10N on the surface of moon will be  1/6 × 10N = 1.67N.

Weight of the body is equal to product of mass and acceleration due to gravity.= Kg × m/s² = N (Newton).

One kilogram weight is that gravitational force which acts on a body of mass 1 kg.
g = 9.8 m/s²
1 kg wt =  9.8 N
This means that the weight of 1 kg mass is 9.8 N.

When an object is thrown up its speed decreases with height as gravitational force acting on it is negative. After attaining maximum height object start falling down ward with increasing speed as the gravitational force acting is positive.