Presentation on theme: "Teacher Page IV. Force, Motion and Mechanical Energy C. Interactions of force and motion State Standards 1.5; 4.1; 1.10 7th grade assessment Students should."— Presentation transcript:
Teacher Page IV. Force, Motion and Mechanical Energy C. Interactions of force and motion State Standards 1.5; 4.1; 1.10 7th grade assessment Students should be able to determine the amount of work done when an object is moved or when a task is performed. View lesson before using with students. Sample questions and answers appear with mouse click or automatically.
When is Work Really Work? In science you do work on an object when you exert a force on the object that causes the object to move some distance. If the object does not move, no work is done no matter how much force is exerted.
How can you determine how much work is done on an object? Which do you think involves more work: lifting a 100 newton box a meter off the ground or lifting a 200 newton box to the same height? Is it more work to lift a box from the ground to a table or from the ground to the top story of a building?
The amount of work you do depends on both the amount of force you exert and the distance the object moves. To help rearrange the furniture in your classroom, you exert a force of 20 N to push a desk 10 m. How much work do you do?
The amount of work done on an object can be determined by multiplying force times distance. Work = Force x Distance Write the formula in your science journal
Substitute and Solve To help rearrange the furniture in your classroom, you exert a force of 20 N to push a desk 10 m. Work = 20N x 10m Work = 200 N. m, which is 200J The answer tells you that the work you do on the desk is 200J
You exert a force of 0.2 N to lift a pencil off the floor. How much work do you do if you lift it 1.5 m Write the formula. Substitute and solve. Work = 0.2 N x 1.5 m Work = 0.3 J