work
What is the SI unit for work?
Joule (J)
What is mechanical advantage?
it is the number of times that the machine increases an input force
How can you tell that work has been done?
If there is no movement, no work is done.
A kilowatt is = to how many watts
1000 watts
Is a gear one of the 6 simple machines
no
What is the unit for measuring power?
Watt (W)
What is power
Power is the rate of doing work
Describe the output to input relationship in real machines.
it is the ratio of the output force to the input force
How could you overcome friction to make a machine more efficient?
use low-friction materials
True or false: An inclined plane wrapped around a central cylinder is a lever.
False
What is the formula for work?
Work= Force x Distance
What is ideal mechanical advantage?
it is the mechanical advantage in the absence of friction
In which direction does net force, that does work, act?
always in the direction of the acceleration. (some of the force must act in the same direction as the object moves)
Why would you use a machine if it does not decrease the amount of work you do?
to reduce the amount of force you must exert
How does friction affect a machine’s efficiency?
Because of friction, the work done by a machine is always less than the work done on the machine
What is the formula for power?
Power= Work/time
What is a fulcrum?
It is a fixed point that the bar rotates around
What is the efficiency of a ideal machine?
100%
How is it possible to exert force and not do any work?
When a force acts on an object, but the object doesn't move
List the six types of simple machines and give at least 2 examples of each.
lever:
Wheel & axle:
Inclined plane
Wedge
Screw
Pulley
true or false: The more efficient a machine is, the closer the actual mechanical advantage is to the ideal mechanical advantage.
True
What are compound machines?
they are combinations of two or more simple machines that operate together
Name the 6 simple machines
lever
Wheel & axle
Inclined plane
Wedge
Screw
Pulley
What are the ways that machines make work easier?
They change the size of a force needed, the direction of a force, or the distance over which a force acts
Describe the machines found in the human body and how each one works.
wedge- teeth
Pulley- Kneecap