120 likes | 383 Views
Fixed and Moveable Pulley Systems. Movable . The fixed pulley is a pulley that is attached to a structure and does not move. It’s main purpose is to change the direction of the force needed to lift a load.
E N D
The fixed pulley is a pulley that is attached to a structure and does not move. It’s main purpose is to change the direction of the force needed to lift a load. A force is exerted downward in order to lift the load upward. The effort force needed does not change.
????? • With a fixed pulley, does it take less force to lift the load with the pulley or without a pulley? A. The force needed to lift a load with the fixed pulley is the same as without a pulley. • With a fixed pulley, how is the direction of the force needed to lift the load different than without the pulley? A. The force is in the opposite direction to the direction the load moves. With the pulley, the force goes down and the load goes upwards. Without the pulley the force and the load are both upwards.
Movable Pulley • In a movable pulley system, the pulley supports the load and is not fixed in place. • In the movable pulley system, the force is applied in the same direction that the load moves. • However, it does require less force to move the load than without using a pulley.
With a movable pulley, does it take less force to lift the load than with the fixed pulley? A. The force needed to lift a load with a movable pulley is less than the force needed without a pulley. • With a movable pulley, how is the direction of the force needed to lift the load different than without the pulley? A. The force is in the same direction as the load moves. The force is up and the load moves up. This is the same results without the pulley.
????? • When would you use a fixed pulley to lift a heavy object? When would you use a movable pulley to lift a heavy object? • The fixed pulley can be used when you want to change the direction of the force. It can use the force of gravity when the person pulls down – their body weight will help pull the rope. The movable pulley can be used to decrease the amount of force needed to lift an object. • Compare the commercial pulleys we used in this activity with the “homemade” pulley we used. Which materials would you rather work with? Why? A. The commercial pulleys are usually better because they produce less friction and are easier to use.
Summary • A fixed pulley makes work easier because you can pull down instead of pushing something up. • A movable pulley needs less effort to lift a load. If a movable pulley and a fixed pulley were both used, what would be the result?!? • A pulley system that would change the direction of the load and decrease the force needed.