Forces Flashcards
what are forces
pushes or pulls
Forces can :
change the size or shape of an object
change the speed things are moving (make them faster or slower)
change the direction of a moving object
what is the unit for measuring forces
newton (N)
what are contact forces
a force that acts at the point of contact between two objects
what do contact forces need to do
need to tough the thing that they are affecting
examples of contact forces
friction, air resistance, water resistance, upthrust
what are non-contact forces
forces that don’t need to tough the ting that they are affecting
examples of no-contact forces
magnetism, gravity, static electricity
example of balanced forces
if the upwards and downwards forces on a balloon are balanced. the balloon will not move.
the upwards force- upthrust and the downwards force- force from the string are balanced
why doesn’t a rocket in space need to use its engine to keep moving.
because there is no air in space, so there is no air resistance to slow it down.
example of balanced forces in water
if you are floating in a swimming pool, your weight and upthrust are balanced
how can you decide if something is floating
by working out its density
what is density
the mass of a certain volume of something
how can density be calculated
density = mass divided by volume
unit for density
g/cm3
density of water
1g/cm3
when will an object sink or float
if an object has a density less than 1g/cm3it will float
if the density is greater than 1g/cm3 it will sink
how will elastic materials stretch with a force
stretch with a force and then return to their original shape when the force is taken away
how will plasticise materials stretch with a force
will stretch with a force but they will not return to their original shape afterwards
what is used to measure a force and why
a force meter, because they have springs in them that are elastic
what is mass
the amount of substance in your body
what is mass measured in
kilograms (kg)
what is the weight
a force caused by gravity pulling on your body
what will change/remain when you move an object
its mass will not change but its weight depends on the force of gravity
weight difference between earth and moon
an object on the moon would have a smaller weight than on earth, because the moons gravity is not as strong as earths
what does gravity pull on every kilogram with
a force of 10N
what is friction
a forced caused by two things rubbing together
types of friction
air resistance and water resistance sometime called drag
friction can :
slow things down, wear things away, produce heat, make an noise
when is friction helpful
your shoes grip the floor
tyres and brakes use friction
pencils write because of friction
when is friction not helpful
parts of engine wear away
makes bicycles harder to pedal
how can friction be increased
by using rough surfaces or by using materials like rubber that have a lot of friction
how can friction be decreased
by using smooth surfaces or by lubrication like oil and grease.
how do you work out speed
distance travelled divided by time taken
what is the thinking distance
the distance the car travels while the driver is deciding to stop
what is the braking distance
the distance it travels while it is slowing down
how do you get the stopping distance
thinking distance + braking distance
when are stopping distances longer
if the road is wet or icy, if the car has worn tyres, if the driver is tired or been drinking alcohol
how can a journey be shown
on a distance/ time graph
when a person runs what will it look like on a graph
steep increase
if a person stops what will it look like on a graph
a straight line
when a person walks slowly what will it look like on a graph
steady increase
the steeper the line on the graph …..
the faster they are moving
