What is work done?
Another name for the amount of energy you transfer when you act on something with a force
What is the equation for work done?
Work done = force x distance in the same direction as the force
W = Fd
J = N*m
What is power?
The rate at which energy is transferred
What is the equation for power?
Power = work done / time
What are the two types of forces?
Contact e.g. upthrust, normal contact force, friction
Non contact e.g. magnetism, gravity, static electricity
How can energy be transferred?
Forces doing work
What are non contact forces caused by?
Interacting fields e.g. the gravitational attraction between objects is caused by their gravitation fields interacting. Interacting magnetic fields cause attraction or repulsion between magnetic objects. Electrostatic forces cause attraction and repulsion between electrical charges because their electric fields interact.
What is an interaction pair?
Whenever two objects interact, both objects feel and equal but opposite force. This pair of forces is an interacting pair
What are resultant forces and free body diagrams?
A resultant force is the overall force acting on an object
Free body diagrams show all the forces acting an object
What are vector diagrams?
Diagrams used to find resultant forces
They are scale diagrams where the components are drawn nose to tail to each other and the resultant force joins betweens them.
How do you resolve forces?
You resolve forces by splitting them up into their x and y components at right angles
What are forces?
Pushes and pulls measured in Newtons. They are drawn with arrows. The size of the arrow shows the size of the force. A free body diagram shows all the forces acting on an object. Forces in the same direction add up and forces in opposite directions partially or completely cancel out. The resultant force is the overall force.
What is a moment?
The turning force around a pivot. Its units are Newton metres. Moments can be increased by increasing force or distance
What us the equation for moments?
Moment = force x perpendicular distance from pivot M = Fd Nm = N * m
What is the principle of moments?
For an object in equilibrium: sum of clockwise moments = sum of anticlockwise moments
What are levers?
A lever is a long bar that pivots. Levers transfer the turning effect of a force. When you push down on one side, you are applying force. The object for the other end (the load) moves up. Using a lever magnifies the force and makes objects easier to move.
What are gears?
Circular cogs with teeth around their edge. The teeth can interlock so that turning one gear causes another to turn as well. A gear spinning clockwise will make the next gear spin anti-clockwise. They transmit the rotational effect of a force from one place to another.
A force applied to a small gear creates a small moment. The gear applies the same force to the next gear. If the next gear is larger, the force is applied further from the pivot, so the moment is larger.
Interlocked gears will rotate at different speeds - the larger the gear, the slower it spins.