A ball is dropped from the top of a cliff. By the time it reaches the ground, all the energy in its gravitational potential energy store has been transferred into its kinetic energy store. If the ball is travelling at 20 m/s when it hits the ground, what height was it dropped from? (Assume that the gravitational field strength is 10 N/kg.)
Answers
Answer:
Explanation:Before you release the ball from a height h, the ball has a potential energy of mgh where m is the mass, g the acceleration due to gravity and h the height above the surface. The kinetic energy is zero since the ball is at rest (in your hand or on some surface at rest.
When the ball hits the ground, potential energy is zero and Kinetic energy becomes maximum and is 0.5 mv^2 where v is the velocity.
We know that energy is conserved and so can write
mgh = 0.5 mv^2
v^2 = 2gh
We can also state that at any point between the point of release at a height h from the ground and the ground, the sum of potential energy and kinetic energy remains constant.
Answer:
5km
Explanation:
In the question, 10N is not equal to 10kg/kgf .kgf is called kg force. However, you need to divide 100kg/kgf by 20 which gives the answer 5km. Hence, the answer is that the ball was dropped from 5km.
Working:
100000/20
=5000m
=5km