Forces and motion Flashcards
Put the correct words into the speed formula triangle
Speed
Distance
Time
What are the three most common units of speed
m/s metres per second
mph miles per hour
km/h kilometres per hour
What is a force?
A push or a pull
What is the SI unit for force
Newtons (N)
What instrument measures a force
A newton meter
Identify the 5 actions which are the result of applying a force
- Speed up or move more quickly
- Slow down or stop moving
- Change direction
- Turn
- Change shape
What type of forces produce no change in movement
Balanced forces
What type of forces produce a change in movement
Unbalanced forces
Describe deforming
Changing the shape of something by applying a force
Describe the action of a spring when a force is applied
The spring will deform by stretching or compressing when a force is applied
Springs are elastic- they usually spring back to their original shape
What does the k stand for in Hooke’s law
k = spring constant
What does the F stand for in Hooke’s law
F = force
What does the e stand for in Hooke’s law
e = extension
What is the formula for Hooke’s law
F = K x e
How do two springs acting in series act?
The two springs are joined together and extend the same amount as each individual one would with the same force
eg two springs 10cm long would extend 20cm
How do two springs acting in parallel act?
The two springs are next to each other and each extends half the amount than an individual would with the same force
eg 2 springs 10cm long would extend 5cm
Which direction does friction always act in?
The opposite direction to movement
Give some examples of the positive action of friction when riding a bike
It allows you to start, slow down and stop when you are on a bike
It allows the tyres to grip the road so you can move forward
It acts at the brakes as they grip the wheel rim making you slow down/stop
It allows you to grip the handlebars so you stay on
Describe friction
It is a force which acts between surfaces trying to stop objects sliding past each other.
Give some examples of the negative action of friction when riding a bike
Friction always wastes energy so the some of effort you put into to riding your bike will be wasted and limits your top speed
Friction between the moving parts of the bike wastes energy
Air resistance is a type of friction and this slows you down as well.
Top cyclists try to overcome air resistance with their clothing and helmet design being the most aerodynamic that they can. It is also why they try and cycle as close behind someone as they can.
Explain what air and water resistance do to moving objects
They slow them down.
Sometimes called drag air and water resistance push against a moving object in the opposite direction to the movement
They a type of frictional force
Cars boats aeroplanes and other moving objects which need to move fast are designed to be streamlined to slip through the air or water with too much resistance.
Explain how a parachute slow down a person falling through the air.
- Without a parachute the air resistance of the person is a smaller force than the weight (gravity) acting down and so the person falls faster.
- When the parachute opens the air resistance increases and is now larger than the weight and so the person slows down
- The air resistance and the weight become balanced and so the person falls at a steady speed.
- When the persons lands the force acting up from the ground balances their weight.
Identify the two factors which make up stopping distance in a vehicle.
- Thinking distance
- Braking distance
Explain the factors which can affect thinking distance when stopping a vehicle
- Speed, the faster you are moving the further the vehicle will travel
- Driver awareness, How much attention you are paying. This is affected by alcohol, drugs, tiredness and sometimes distractions
Explain the factors which can affect braking distance when stopping a vehicle
- Speed - the faster you are going the longer it takes to stop
- Brakes - if the brakes are worn out they will not work as effectively
- Tyre quality - worn tyres do not grip the road as much so less friction
- Weather conditions - water snow and ice decrease the friction on the road surface
- The road surface, some surfaces are more grippy but leaves, oil spills, muck on the road all reduce friction.
