Chapter 12

Wedge

A device that is thick at one end and tapers to a thin edge at the other end.

Pully

A grooved wheel with a rope or cable wrapped around it.

Screw

An inclined plane wrapped around a cylinder.

How can you determine the amount of work done on an object?

The amount of work done on an object can be determined by multiplying force times distance.

In which of the following situations is work being done: rolling a bowling ball, pushing on a tree for ten minutes, kicking a football?

Work is being done in rolling a bowling ball and kicking a football.

Inclined plane

A flat, sloped surface.

In what three ways can machines make work easier?

A machine can make work easier by changing either force, distance or direction.

What is a machine?

A machine is a device that allows you to do work in a way that is easier or more effective.

Compound machine

A machine that utilizes two or more simple machines.

What is the mechanical advantage of a machine?

A machine's mechanical advantage is the number of times a machine increases a force exerted on it.

How is a real machine like an ideal machine, and how is it different?

A real machine is like an ideal machine, because they work the same way. But they are different, because an ideal machine doesn't have the interference of friction and has 100% efficiency, while a real machine has the interference of friction and has an efficiency that is less than 100%.

Lever

A rigid bar that is free to pivot, or rotate, on a fixed point.

How does a screwdriver make work easier?

A screwdriver make work easier by changing the force. The output force is greater than the in put force when you are using a screwdriver.

What is an ideal machine?

An ideal machine is a machine with 100% efficiency but doesn't exists.

Is more work done when a force of 2N moves an object 3m or when a force of 3N moves and object 2m? Explain.

Both of the ways have the same amount of work done, because when you plug the numbers into the work formula, they get the same results.

What must you know in order to calculate a machine's efficiency?

I must know the input and output work to calculate a machine's efficiency.

What is a joule?

One joule is the amount of work you do when you exert a force of 1 Newton to move an object a distance of 1 meter.

How are power and work related?

Power and work are related, because in the process of calculating power, work is needed.

What is power?

Power is the amount of work done on an object in a unit of time.

Fulcrum

The fixed point that a lever pivots around.

If a machine has an input force of 40N and an output of 80N, what is its mechanical advantage?

The mechanical advantage is 2.

What is the mechanical advantage of a machine that changes only the direction of the applied force?

The mechanical advantage of a machine that changes only the direction of the applied force is 1.

In order for work to be done on an object, what must happen to the object?

The object must have moved in the same direction the force has exerted.

Wheel and axle

Two circular objects fastened together that rotate about a common axis.

What is work?

Work is when you exert a force on an object that causes the object to move some distance.