motion and forces Flashcards
(13 cards)
what is the law of conservation of energy
energy cannot be created or destroyed, only transferred
name and give descriptions of the 5 main contact forces
friction - force that prevents objects moving or slows them down when moving
drag - caused by friction from air
upthrust - is produced by water pushing upwards on an object
surface tension - this helps raindrops keep their shape and allows some insects to move on waters surface
reaction force - the force acting in the opposite direction
name and give descriptions of the 3 main non-contact forces
gravity - this is the force that pulls objects down to the centre of the planet and which gives them weight. gravity us present between any two objects.
magnetic force - the force produced by a magnet that affects magnetic materials such as iron. usually only works over a short distance
electric force - from static electricity that can attract objects. this also tends to act over a short distance
formula triangle for distance
distance = speed x time
what are forces measured in
newtons
units for mass
g/kg
units for weight
newtons (N)
how do you convert mass into weight on earth
on earth, 100g is equal to 1N and 1kg is equivalent to 10N
what can forces do to objects
change their shape, direction and speed
when forces are in equilibrium, what does this mean
that the forces are all equal or balanced. the resultant force would be zero N.
state Hooke’s law
the extension of a spring is proportional to the force added
name 4 pros and cons of friction
pros - car tyres can push forward so car can move, friction helps brakes, shoes grip so we can walk, allows you to hold things
cons - slows moving things down, wears engines out, wears tyres and soles of shoes out, generates excess thermal energy
what is the stopping distance
the time it takes to stop a car
