When is work done on an object?
When a force causes an object to move along the line of action of the force
What happens when work is done?
Energy transfers take place within the system
Why does moving an object require work?
Because energy is needed to move the object.
how many Joules does 1 newton metre equal to
1 joule
Give an example of energy transfer when work is done
The force of friction causes energy to be transferred to thermal energy
What happens when a force is used to move an object?
Work is done on the object, which transfers energy. The movement of the object from its starting point to its final position is called displacement
What must happen to change the shape of an object?
more than one force must be applied
eg. sprint must be pulled from both ends to stretch it
what is elastic deformation
when an object returns to its original shape after force is removed
what is inelastic deformation
when the object doesn’t return to its original shape after the forces are removed
What is the relationship between extension and force for an elastic object?
linear relationship: extension is directly proportional to force
What happens if a spring is stretched beyond its limit of proportionality?
-It becomes inelastically deformed, so the spring won’t return to its original length after the force is removed
-If stretched even further, it can permanently deform or break
What is the spring constant
A measure of how stiff a spring is:
larger spring constant = stiffer spring.
What type of energy is stored when a spring is stretched or compressed?
elastic potential energy
what is the unit for moment
Nm
what is a moment of a force
The turning effect of a force around a pivot.
When do moments occur?
When a force causes an object to rotate about a pivot point.
What equation must be true for a balanced object?
F₁ × d₁ = F₂ × d₂
What can be said about the moments acting on a balanced object?
the total clockwise moment about the pivot equals the total anticlockwise moment about that pivot
What do gears do?
changes the size of a force, the speed or the direction of rotation
Why are levers useful?
They act as force multipliers, allowing a smaller force to lift a larger load, and it can change the direction of the force
How does a lever reduce the effort needed to move a load?
When the applied force moves a further distance than the transmitted force, the force is decreased
What happens if a lever is used to increase the speed or distance of movement?
the applied force is bigger than the transmitted force
what are 3 parts that make up a lever system?
- load
- effort
2.pivot
What do gears do in terms of forces and rotation?
They transfer rotational motion
Larger gears turn slower but with more force
Smaller gears turn faster but with less force
