Physics Y10 Forces 2 Flashcards
formula for momentum
momentum = mass * velocity
what is momentum
a measure of the tendency of an object to keep moving or how hard it is to stop moving
what is momentum measured in
kilogram metres per second (kgm/s)
what is the conservation of momentum law
total momentum before is equal to total momentum afterwards, unless acted on by an external force
what is an impact force
a force causing a change in momentum to an object
formula for impact force
force = change in momentum/time
what is the stopping distance
how far a vehicle travels until it stops
how do you calculate stopping distance
thinking distance + braking distance
what factors affect thinking distance
- speed of vehicle
- how intoxicated the driver is
- the driver’s concentration
what factors affect the braking distance
- speed of vehicle
- mass of vehicle
- condition of brakes
- condition of tyres
- condition of road
what are stopping distances for 20 mph
6m thinking, 6m braking
what are stopping distances for 30 mph
9m thinking, 14m braking
what are stopping distances for 40 mph
12m thinking, 24m braking
what are stopping distances for 50 mph
15m thinking, 38m braking
what are stopping distances for 60 mph
18m thinking, 55m braking
what are stopping distances for 70 mph
21m thinking, 75m braking
how will increased viscosity affect terminal velocity
it will decrease
how will decreased mass affect terminal velocity
it will decrease
what is terminal velocity
the velocity reached by an object when the drag force on it is equal and opposite to the force making it move
what is Hooke’s law
the more force that is put on materials, the more they extend
when is Hooke’s law true
as long as the elastic limit is not exceeded
what happens after the elastic limit is exceeded
the material no longer hows elastic behaviour and is permanently deformed (does not return to original position when force is removed)
equation for Hooke’s law
force = extension * spring constant
what does a higher spring constant mean
stiffer spring
what axes do force and extension go on on a graph
force - y axis, extension - x axis
what does the gradient on a force-extension graph show
the spring constant
what does a steeper curve mean on a force-extension graph
a stiffer spring
what is a lever
a long bar that pivots
what happens when you apply a force to one side of a lever
the other side moves up
how is using a lever helpful
it can magnify forces, making objects easier to move
what is a moment
a turning force
formula for moment
force * perpendicular distance from pivot
units for moment
newton metres (Nm)
what can gears do
- increase speed
- increase force
- change direction
what happens as force increases on a gear and why
speed decreases because work done = force * distance (work done stays same, so distance has to decrease)
what will a bigger gear do
higher force, lower speed
what will a smaller gear do
lower force, higher speed
what directions do two touching gears go
in opposite directions
+centre of mass stuffs
