Work and Simple Machines

What is work? The scientific definition of work is: the transfer of energy to an object by using a force that causes the objet to move in the direction of the force For work to happen, you need two things: 1) the object moves as a force is applied and 2) the direction of the object’s motion is the same as the direction of the force

What is work? Putting forth a lot of effort or energy DOES NOT mean you are doing work. (Ex. Holding something for a long time.) Transfer of energy is another way to tell work has been done. Bowling transfers your energy to the ball, so the ball has kinetic energy.

Doing Work?

Doing Work?

Work or Not? According to the scientific definition, what is work and what is not? a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor

Work or Not? According to the scientific definition, what is work and what is not? a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor

What’s work? A scientist delivers a speech to an audience of his peers. A body builder lifts 350 pounds above his head. A mother carries her baby from room to room. A father pushes a baby in a carriage. A woman carries a 20 kg grocery bag to her car?

What’s work? A scientist delivers a speech to an audience of his peers. No A body builder lifts 350 pounds above his head. Yes A mother carries her baby from room to room. No A father pushes a baby in a carriage. Yes A woman carries a 20 km grocery bag to her car? No

What’s work? A student 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 and walks across the room at a constant speed. A rocket accelerates through space.

What’s work? A student applies a force to a wall and becomes exhausted. No A book falls off a table and free falls to the ground. Yes A waiter carries a tray full of meals above his head and walks across the room at a constant speed. No A rocket accelerates through space. Yes

Formula for work Work = Force x Distance (j) = (n) x (m) The unit of force is newtons The unit of distance is meters The unit of work is newton-meters One newton-meter is equal to one joule So, the unit of work is a joule

How can we use the triangle for the work equation? Formula for work How can we use the triangle for the work equation? W F D

W=FD Work = Force x Distance Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done?

W=FD Work = Force x Distance Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? 200 joules (W = 20N x 10m)

W=FD When pushing a shopping care 10 m you did 100 J of work. How much force was required?

W=FD When pushing a shopping care 10 m you did 100 J of work. How much force was required? 100 J/10 m = 10 N