An object of mass 100g projected vertically upwards from the ground level has a velocity of 20ms-1 at a height of 10m. calculate its initial kinetic energy at the ground level.[g = 10ms-2, neglect air resistance]
- 10 J
- 20 J
-
30 J
- 50 J
The correct answer is: C
Explanation
Using, v2 = u2 - 2gx(20)2 = u21/2 x 10 x 10
u2 = 600(m/s)2
initial K.E = - mu2
= \(\frac{1}{2}\) x 600
= 30 J