Forces, Motion And Energy Flashcards
What factors affect vehicle stopping distance
Thinking distance:
Speed : Faster the speed, the longer it takes to stop.
Reaction time: Tiredness, drugs, alcohol
Braking distance:
Speed : Faster the speed, the longer it takes to stop.
Mass : the heavier it is, the longer it takes to stop
Grip: Road condition, e.g. Icy, dusty, stoney, weather conditions, e.g. Windy, rainy
Definitions of : GPE KE and work
GPE: it is the energy an object has because of its height in a gravitational field.
KE : it is the energy of an object due to motion
Work : is the amount of energy transformed when a force moves.
GPE = KE = work (pendulum)
What is power
- it is the rate of transfer of energy
- measures how quickly work is done
E.g. Running up stairs requires more power than walking up that same flight of stairs.
What are the 2 types of deformation
Elastic : returns to its original shape
Plastics : permanent change
What is Hooke’s 1st Law
Providing an object is within its elastic limit, extension is directly proportional to the force that produces it.
What is hysteresis
Materials which don’t obey hooke’s law e.g. Rubber (elastic bands), polythene (relatively easy to stretch at first as chains uncoil, then it becomes much stiffer)
What is momentum/inertia
Momentum = a measure of how hard something is to stop Inertia = is a measure of how hard something is to move
2 types of collisions
Elastic collisions : between 2 rigid bodies e.g. Pool balls. MU + mu = MV + mv (m = mass v = final u = initial)
Inelastic collisions : form 1 single object. MU + mu = (M + m)V
Safety features
Seat belts : stretch slightly, preventing you from hitting the windscreen with the same force experienced by the car
Crumple zones : increases the amount of time it takes to actually stop.
Reduces acceleration and the force acting against the car.
Air bags : increases time it takes you to stop relative to the car.
Inner planets
(Mercury Venus earth mars)
- terrestrial planets
- Rocky and dense
- molten metal core (Iron)
Outer planets
(Jupiter Saturn Uranus Neptune)
- large
- made of gases and liquids with no solid surface
- tumultuous atmosphere (windy, violent storms)
Orbits
An orbit is a balance between the forward motion of an object and a force pulling it inwards.
Planets/moons: near circular (sun/planet is centre)
Comets: very elliptical (sun is at 1 focus if the orbit)
Gravity
- depends upon mass and distance
- speed depends on the radius of the orbit
Why must there be a top speed for any car
Air resistance increases with speed until air resistance equals maximum forward force then acceleration is zero.
what is terminal velocity
when forces are balanced, acceleration is 0 and speed is constant
