Lesson: Mechanical Energy and DynamicsPhysics
In this lesson, we will learn how to apply the principle of the conservation of energy to systems involving kinematics, resistive forces, and other variable forces.
Sample Question Videos
A boy throws a ball of mass 0.25 kg vertically upward with an initial speed of 20 m/s. The ball moves vertically upward, comes instantaneously to rest, and then accelerates vertically downward and returns to the point from which it was thrown. When the ball returns to its original position, its speed is 17 m/s. How much work was done by air resistance on the ball during its flight?
A crate of mass 50 kg is being pushed across a rough surface at a steady 8.0 m/s. The crate is then released and comes to a stop in 10 seconds. What is the average rate at which the frictional force on the crate removes kinetic energy from it?
An 80.0 kg sprinter accelerates from rest to 12.0 m/s in 2.90 s.
What is the average power output of the sprinter in watts?
What is the average power output of the sprinter in horsepower? In metric horsepower, 1 hp = 735.5 W.