forces Flashcards
explain vector quantity + example
they have magnitude and direction ( force velocity acceleration, momentum , displacement)
explain scalar quantity + example
only magnitude , no direction (speed distance, time mass temperature)
how are vectors shown
arrows, length of arrow shows magnitude, direction shows direction of quantity
force
push of pull on an object caused by an interaction with something
contact force
2 objects need to be touching for force to act (air resistance , friction, tension in rope)
non contact force
objects dont need to touch for force to act (magnetic force, gravitational, electrostatic)
interaction pair of forces
pair of forces equal and opposite - act on 2 interating objects
interaction pair of forces (non contact)
earth and sun ( attracted by a gravitational force ) equal but opposite force of attraction
interaction pair of forces (contact)
chair exerts force on ground , ground pushes chair with the same force - equal but opposite force felt by ground and chair
graviational force
force of attraction between masses , on surface of a planet it makes everything fall to the ground and gives everything a weight
mass
amount of stuff or matter in an object - same value anywhere in all locations
weight
force acting on an object due to gravity- pull of gravitational force on object - force caused by gravitational field around earth
what does gravitational field strength vary with
location- its stronger the closer you are to the mass causing the field, stronger for larger masses
what does weight of object depend on
strength of gravitational field strength at location of object - weight of object changes with location
example of how weight can vary
object on moon will weigh less on moon-1.6 n- than earth because gfs on moon is less than gfson earth-9.8n-
how and what is weight measured in
measured in newtons with calibrated spring balance or newtonnmeter - measured from centre of mass- for uniform object, it will be at the centre of the object
what is mass measured in
kilograms, with a mass balance - mass is not force
how to calculate weight
mass x gravitational field strength (weight and mass is directly proportional)
explain what free body diagram shows
size of arrows show relative magnitude of forces. directions show the direction of the forces acting on the object
resultant force
overall force on a point or object- if you have a number of forces acting at a single point , you can replace them with single force which has the same effect as all the original forces all together - this single force is known as the resultant force
how is overall effect of forces found
if they all are parallel , effect is found by adding those going in same direction - those going in an opposite direction (consider vertical and horizontal directions separately)
what happens when a resultant force moves an object
work is done- when a force moves an object through a distance , energy is transferred and work is done on the object
to make an object move a force must be applied . the thing applying the force needs a source of energy, the force does work to move the object and energy is transferred from one source to another
example of energy transfer through forces
you push something along rough surface, work is done against frictional forces, energy is transferred to kinetic energy store of object bc it is moving, energy is transferred to thermal energy store(due to friction) causing overall temperature of object to rise
how to calculate work done
force x distance is work done
one joule of workis done when a force of one newton causes an object to move a distance of one metre (1 JOULE IS 1 NEWTON METRE)
how to use scale drawings to find resultant force
1- start by drawing a scale drawinf of the forces acting
2- sensible scale e.g. 1n-1cm
3- draw resultant from tail of first arrow to tip of last arrow
4- measure length of resultant with ruler , use scale to find force in N
5- use protractor to measure direction as a bearing (clockwise from north )
what does it mean if an object is in equilibrium
forces on it are balanced, if all forces combine to give a resultant force of 0 the object is in equilibrium
how would you find a missing force given that the object is in equilibrium
draw the forces you know , join end of last force to the start of the first force , the line is the missing force so you can measure its size and direction
how do you split a force into components
forces at awkward angles can be split into 2 components at right angles to each other - acting togrther these components have the same effect as a single force- (draw on a scale grid, draw the force to scale , add horizontal and vertical components to grid line , measure them)
when a force is applied to an object, it may cause it to stretch compress or bend , how does this happen?
stretching compressing or bending transfers energy, you need more than 1 force acting on the object ,
how can you tell if an object has been elastically deformed
if it can go back to its original shape and length after the forc has been removed
how is an object inelastically deformed
if it does not return to original shape and length after force has been removed
how is work done/ energy transferred to an elastic potential energy store
work is done when a force stretches or compresses an object and causes energy to be transferred to elastic potential energy store of object, if it is elastically deformed, all energy is transferred to object’s elastic potential energy store
