p9 forces Flashcards
what is a force?
a push or pull that acts on an object due to the interaction with another object.
it is a vector quantity.
what is a contact force?
when objects are physically touching
e.g. friction, air-resistance, water resistance, tension, normal contact force
what is a non-contact forces?
when the objects are physically separated and when objects do not need to be in contact for the force to act
(e.g. gravitational force, electrostatic force and magnetic force)
what is the same about the interaction pair of forces when two objects interact with each other?
what is different about the interaction of forces when two objects react with each other?
why?
the forces are the same size
forces are in opposite directions
because when an object exerts a force on another object, it will experience and equal and opposite force.
What is the resultant force?
a single force that has the same effect as all the original forces acting together
The resultant force is:
- the sum of the magnitudes of the forces if they act in the same direction
- the differences between the magnitudes of the forces if they act in opposite directions
What happens when the forces on an object are “balanced”
the resultant force will be zero.
Free body diagrams
- are used to show all of the forces acting on a single object
a dot/circle is used to represent the objects, with the forces drawn as arrows. - the arrow length shows the magnitude of the force
- the arrow direction shows the direction of the force
Gravity
The force of gravity close to the Earth is due to the gravitational field around the Earth.
what is the name for the force acting on an object due to gravity
weight
what instrument can be used to measure the weight of an object
newton meter
what is the centre of mass?
the point at which the weight of an object can be considered to act
Work done and energy transfer
When a force causes an object to move through a distance, work is done on the object.
So a force does work on an object when the force causes a displacement of the object.
so work is NOT done when the object does not move in the direction of the force.
Work done against the frictional forces acting on an object causes
a rise in the temperature of the object.
the unit of work
One joule of work is done when a force of one newton causes a displacement of one metre.
1 joule = 1 newton-metre
What is elastic deformation
an object can go to its original shape and size when deforming objects are removed
