## Power

(1) What is the average power developed by a force of intensity 100N over a course of 20m over a period of 2s?

(2) A 1kg mass block has a constant acceleration of 3m / s². Since this part of rest, what is the instantaneous power of the block after 10s?

*To make this calculation, it is necessary to know the force exerted on the block and the velocity at the requested time.*

*Knowing Strength and Instantaneous Speed:*

## Energy

(1) What is the energy of a 1kg mass body that travels at a constant speed of 10m / s?

(2) A 10kg car mass travels at a speed of 12m / s when it sees a pedestrian and brakes to a stop. What work is done by the car brakes?

*For the Kinetic Energy theorem:*

(3) A man falls from a height of 100m. What is your speed on reaching the ground?

*By the principle of energy conservation:*

(4) A 12kg block falls from a height of 20cm on an elastic constant spring k = 500N / m in its resting state. What will be the compression in the spring?

*We must use the principle of energy conservation. But we know that when the block falls, its gravitational potential energy becomes kinetic energy and when the block reaches the spring, the kinetic energy becomes elastic potential energy, so:*

, the initial kinetic energy in this case is equal to the final kinetic energy of the situation in which the block falls.