YAY work

Good day everyone. On Friday we started a new chapter in physics, all to do with work, power and energy. We started by listing what we knew about the topic and came up with several pieces of information including:

• It takes energy to do work
• You get energy from food 
• Electricity is a form of power (Steam power, coal power)

We also discussed kinetic and potential energy, kinetic energy being the amount of energy an object has while it is in motion and potential energy being the amount of stored energy and object has.

Example of Potential Energy:

Holding a football above the ground, has potential energy due to the force of gravity because if you let go, the ball will fall to the ground. The higher you hold the ball the more potential energy the football has.

Work:

After discussing the informtion we already knew about the subject we finally defined Work as the product of an applied force and the displacement of an object in the direction of the applied force. In other words it is when we apply a force to an object and the object moves in the direction the force was applied or in the opposite direction.

W=Fd 

W= work F=force d=displacement

Unit = Joules (J)

If there is no applied force upon an object or there is a displacement of zero, no work has been done. For example if you pushed all day on a wall but the wall has not moved, you have made no progress therefore you have done no work.

Also no work has been done if the force being applied and the displacement of the object are perpendicular to one another. For example a satellite orbiting the earth, the satellite is moving forward around the earth but gravity is pulling the satellite down, by definition it is not work.

Positive work- when the applied force and the displacement act in the same direction

Negative work- when the applied force and the displacement act in opposite directions

We followed all of this great knowledge with some examples.

1. Find the work required to lift a 3.0x10^3 kg object to a height of 5.0 m?

F=mg                                                   W=Fd

F= (3.0x10^3 kg)(9.8 N/kg)                W=29400 N x 5.0 m

F= 29400 N                                         W=15000 J

d= 5.0 m

W= ?

2. A person pushes a loaded box 55.0 m by exerting a horizontal force of 35.0 N on the box. How much work is done?

d= 55.0 m                                            W=Fd

F= 35.0 N                                            W= 35.0 N x 55.0 m

W= ?                                                    W= 1925 J = 1930 J (significant digits)

(If the object is not being lifted we do not have to worry about mass x gravity as in example 1.)