Conservation of Energy: The Inclined Plane

Background: In the absence of friction, the work done to pull an object up an incline plane is equal to the work done to lift the object up the same vertical distance. That is, the change in gravitational potential energy is independent of the path taken to get to the height.

When lifting an object straight up, work is only done against gravity. The work done by the moving force is equal to the change in gravitational potential energy if the object is moving at a constant speed. In order to move an object up an inclined plane, work must be done against the gravitational force AND friction on the inclined plane. The work done by the pulling force will be equal to the negative work done by friction, if the object is moving at a constant speed.

Objective: To verify the law of conservation of energy
Materials:
Inclined plane, smooth wood block, spring scale, meter stick

Set up:
[pic][pic]

Procedure: 1. Make sure the incline plane and block are clean. 2. Set the incline so that the block just slides down. Measure the length of the incline and the height of the incline. Record in the data table. 3. Place the block at the bottom of the incline. 4. Hook the spring scale to the block and pull the block up the plane at a constant velocity. Read and record the force measured by the spring scale. (This force is equal to the component of the weight directed down the incline plus the frictional force acting on the block down the incline) [pic] 5. Place the block at the top of the incline with the spring scale attached. Let the block slide down the incline at a constant velocity. Read and record the force measured by the spring scale. (This force is equal to the component of the weight directed down the incline plane minus the frictional force directed up the incline plane)
[pic]

Data: