Home
/
Physics
/
A ball is held at rest above the ground. The total energy of the ball at this point is 70 J. The ball is then dropped. What must be the total energy stored by the ball just before it hits the ground? (Ignore air resistance)

Question

A ball is held at rest above the ground.
The total energy of the ball at this point is 70 J.
The ball is then dropped.
What must be the total energy stored by the ball just before it hits the ground?
(Ignore air resistance)

A ball is held at rest above the ground. The total energy of the ball at this point is 70 J. The ball is then dropped. What must be the total energy stored by the ball just before it hits the ground? (Ignore air resistance)

expert verifiedVerification of experts

Answer

4.7252 Voting
avatar
HumphreyElite · Tutor for 8 years

Answer

The total energy stored by the ball just before it hits the ground is 70 J.

Explain

The total energy of an object in this scenario, mid-free fall, consists of gravitational potential energy (PE) and kinetic energy (KE). Just before the ball hits the ground, all of its initial potential energy has been converted to kinetic energy, because the ball is no longer elevated above ground (height is virtually zero), and it has reached its maximum speed.<br /><br />Note the Conservation of Energy. This is a principle that states that energy cannot be created or destroyed, only transferred or converted. Therefore, the total energy of the ball at any point in the fall is the same as its original total energy. <br /><br />Given that the ball is initially at rest and after being dropped it's subject to acceleration due to gravity, right before hitting the ground all its potential energy has been converted to kinetic energy while there's no more potential energy left.<br /><br />Since energy is conserved and transferred in this process, we can say the total initial energy is always equal to the total final energy of the system; that is<br />Initial energy("Potential energy") = Remaining energy ("Kinetic energy (the ball at point of hitting ground)") <br /><br />As given, the entire energy of the system is 70J. <br /><br />So, Even just before hitting the ground, the conservation of energy holds, meaning; the energy before the ball was dropped (that's the total energy given as "70J") is still present and it must equal to the total energy when it just about hits the ground.<br /><br />Therefore, the energy stored in the ball before hitting the ground must be 70J as well
Click to rate:

Hot Questions

More x