Work and Power Work is done when a force is exerted on an object and the object moves a distance x. Work = force ·distance W = F · d units: N·m = Joule Work is a scalar quantity. For work to be done, Force exerted must be in same linear plane as distance.
Work When you hold something, are you exerting a force on the object? When you hold something, are you doing work? If you set the object on a table, does the table exert a force on the object? Does the table do any work? Yes. No. Yes. No. When you hold something, then, you are not doing work either.
Work
Work Work is only done by a force on an object if the force causes the object to move in the direction of the force. Work: force needs to cause the displacement
Quick quiz: kahoot.it A teacher applies a force to a wall and becomes exhausted. A book falls off a table and free falls to the ground. A waiter carries a tray full of meals above his head by one arm straight across the room at constant speed. (Careful! This is a very difficult question that will be discussed in more detail later.) A rocket accelerates through space.
Work When a force is applied at an angle, use the component of the force in the direction of motion. W =F cosq(Dx)
Work Example 5A p.169
Copy and solve problem using guess method in notebook
Bell ringer: copy problem and solve using guess in notebook Sheila has just arrived at the airport and is dragging her suitcase to the luggage check-in desk. She pulls on the strap with a force of 190 N at an angle of 35° to the horizontal to displace it 45 m to the desk. Determine the work done by Sheila on the suitcase.
POWER P = W/t = FDd/t = Power: the rate at which work is done. Unit: J/s = W (watt) 1 kilowatt (kW) = 1000 W 1 horsepower (hp) = 746 watts Horsepower (hp): power produced by a typical British working horse.
Separate sheet of paper Renatta Gass is out with her friends. Misfortune occurs and Renatta and her friends find themselves getting a workout. They apply a cumulative force of 1080 N to push the car 218 m to the nearest fuel station. Determine the work done on the car.
Hans Full is pulling on a rope to drag his backpack to school across the ice. He pulls upwards and rightwards with a force of 22.9 Newtons at an angle of 35 degrees above the horizontal to drag his backpack a horizontal distance of 129 meters to the right. Determine the work (in Joules) done upon the backpack.
During the Powerhouse lab, Jerome runs up the stairs, elevating his 102 kg body a vertical distance of 2.29 meters in a time of 1.32 seconds at a constant speed. a. Determine the work done by Jerome in climbing the stair case. b. Determine the power generated by Jerome.