Скачать или смотреть Work Physics Problems

In this video we work physics problems involving the work done by various forces. We use the definition of work done by a force as well as the work energy theorem.


Problem Timestamps:
0:00 - A 150 g baseball is thrown straight up 7.4 m in the air. Find the work done by gravity on the way up, the way down, and the total work done by gravity.

4:56 - A 55 kg man rides an escalator which makes an angle of 30 degrees with the horizontal. If the escalator takes him to a second floor that is 21 m above the ground level, (a) find the work done by gravity, (b) the work done by the normal force from the escalator step and (c) the work done by friction on his feet.

10:20 - A 10 kg box is pulled 15 m horizontally across the floor with a 30 N force that is 32 degrees above the horizontal. If the coefficient of kinetic friction between the box and floor is 0.40, find (a) the work done by the pulling force, (b) the work done by friction, (c) the work done by gravity, (d) the work done by the normal force and (e) the total work done.

18:47 - A 9 kg crate is moving at 4.5 m/s. A force decelerates the crate to a speed of 2.7 m/s. Find the work done by this force.

22:00 - A sled weighing 550 N is initially moving at a speed of 12.5 m/s and slides to a stop over a distance of 150 m. Find the coefficient of kinetic friction.

27:41 - A spring has a spring force constant of 400 N/m. If you spend 8 J of work to stretch the spring, find how much the spring will stretch.

28:59 - You are skiing at a speed of 7 m/s on a frictionless, flat patch of snow. You then cross a rough stretch of snow for 4 m and return to the frictionless snow at a speed of 3.2 m/s. Find the coefficient of kinetic friction for the rough snow.