A metal sphere of mass 200g falls from a height of 5 m. Calculate velocity with which it will strike the ground.g=10m/s-2

Asked by khushdab | 23rd Apr, 2020, 02:17: PM

Expert Answer:

m = 200 g = 0.2 kg 
h = 5 m 
a = g = 10 m/s2 
u = 0 ( as it is going to fall from a rest position) 
v =?
 
By third equation of motion, we know, 
v2 - u2 = 2as
 
As the sphere is falling from height, equation becomes, 
v2 - u2 = 2gh 
 
v2 - 0 = 2 × 10× 5 
 
v2 = 100 
 
Thus, 
v = 10 m/s
 
OR  
 
There is one more way to solve this problem, 
 
we have mass, height and acceleration due to gravity. 
When the sphere is at height, potnetial energy stored in it is, 
P.E. = mgh = 0.2 x 10 x 5 =10 J 
 
When the sphere strikes the ground, 
K.E. = 1/2 mv2 
 
Thus, at ground K.E. = P.E. 
 
10 = (1/2) x 0.2 x v2 
 Solving this, 
 
v2 = 20/0.2 = 100 
 
Thus, 
v = 10 m/s 
 
Hence, the velocity with which sphere will hit the ground is 10 m/s


Answered by Shiwani Sawant | 23rd Apr, 2020, 07:51: PM