Yr 10 GCSE forces revision Flashcards
Define non contact forces
A non-contact force occurs because either attraction or repulsion between two objects - with no contact. Always a field contact e.g. Gravitational force
Define contact forces
A forces occurs due to the contact between two different objects - no field link. E.g. frictional force
What is a vector quantity?
This is a quantity described with both magnitude (size) and direction. E.g. weight
What is a scalar quantity?
This is a quantity described only of its magnitude (size). E.g. Weight
Give three examples of scalar quantities
Any three of: mass, distance, speed, energy, time, power, force
Give three examples of vector quantities
Acceleration, force, velocity
What is weight?
The downwards force due to gravity
What is up-thrust?
The upward force exerted upwards on an object in a fluid
What is friction?
A resistive force due to 2 objects in contact
What is air resistance?
resistive force due to moving through the air
What is lift?
A force that uses motion for a an object to move up
Give three examples of contact forces
Any three of: Friction, Air resistance, Tension, Reaction
Give three examples of non-contact forces
Gravitational forces, Electrostatic forces, Magnetism
Do forces occur in pairs
Yes!
If a duck is not moving, floating on water, what pair of forces is acting upon it?
Weight downwards, and up-thrust Upwards
What is the difference between weight and mass?
Mass is the amount of matter in something, weight is the force acting downwards due to gravity
What is weight measured in?
Newtons
What is mass measured in?
Kilograms
What is the meaning of gravitational field strength?
How much force gravity exerts per unit mass
What is the unit for gravitational field strength
N/Kg
What increases the Gravitational field strength?
The larger the object and the closer they are
Why are you weightless in space?
There is no forces pushing down on you giving you weight
What is the equation that includes weight?
weight = mass x Gravitational Field strength
What is the definition of the centre of mass?
The point in an object where the weight appears to act
What do you do to find the total force acting against something?
Add the two or more Newtons of the force together.
If, on a Race car, there were 800 newtons of total air resistance and friction in total, and there was 1000N of forward force from the engine what would the resultant force be?
Since forces in different directions cancel out, it would be Forward Force - Backward Force. This means total resultant force would be 200N of forward force
if the resultant force is zero what does this mean?
The object is stationary and is staying stationary or moving objects stay moving at the same speed in the same direction, they are not increasing in speed
If the resultant force of an object is not zero what does this mean
Stationary forces start to accelerate in the direction in the resultant force in the same direction or moving objects start to accelerate in the direction of the resultant force
what is equation for elastic energy?
Elastic potential energy = 0.5 x sprint constant (N/m)x extention^2(m)
What is the equation for force with Spring constant?
Force = Spring constant(N/m) x extention(m)
What is Spring Constant?
It measures how stiff the spring is, the larger the spring constant the stiffer the spring
What is Hooke’s law?
The amount a spring stretches is proportional to the amount of force applied to it
What does it mean about the stretchiness of a spring if it has a high spring constant?
The stretchiness is less, it means it is a stiffer spring
Describe the required practical for F = K x E
Set up a clamp stand, with a spring attached to the top with a hook. You will also need a ruler and some weights. when you add the weights to the hook, the spring will extend, and you measure the extention or you measure the spring, and then the extended spring and minus it from each other.
What is the meaning of a moment?
The turning effect of a force
What is the equation for a moment of a force?
Moment of a force = force x distance
What is a moment measured in?
Newton meters (Nm)
What is the difference between a high and low gear in a bike?
In a high gear, the gears have less teeth which makes the pedal require more force for the wheel to turn.
How do bike gears work?
When the gears turn on the bike from the turning of a pedal, the chain in turn, turns the back wheel which then allows the bike to move
If two gears are touching, and one gear is moving clockwise, in what direction will the other be moving?
Anticlockwise
What three things does a lever consist of?
A pivot, an effort and a load
What is the output of a high gear arrangement?
A high gear produces a high speed and a low turning effect
What is a fluid?
A substance with no fixed shape that can flow
Define the meaning of pressure
The amount of force exerted over a certain area
What is the equation for pressure?
Pressure = force/ area
If there are three holes in a water jug, one at the top, bottom and middle, where would the water flow the fastest?
The bottom, pressure increases with depth
What two things does pressure depend on?
How much force is applied and how big or small the area on which the force is applied is
What is pressure measured in?
Pascals (Pa)
Why does pressure increase and a diver dives deeper in the ocean?
because the water exerts a pressure on their body, the deeper the diver goes, the more water above them and the more pressure there is
What causes the bends for divers
Changes is pressure causes the bends which is also called decompression sickness. This is when a diver returns to the surface too quickly after a dive.
Why do objects in water experience upthrust?
This is because water exerts force on all directions including up
What is the equation that links speed, distance and time?
speed = distance/ time
What is meant by the speed of an object?
How far something moves in a set time
What is speed measured in?
Mph/Kmph or m/s
what is the difference between average speed and instantaneous speed?
Average speed is the speed over a large distance, instantaneous speed is the speed you are travelling at a certain time
What is displacement?
How far something is from the start point
If you are travelling at a constant speed, what would this look like on a distance time graph?
There would be a dead straight line increasing in distance and time.
If you are going faster how would the line look?
The line would be steeper, but still straight if travelling at a constant speed
How would a distance time graph look if you are accelerating?
There would be a sloped line, time would increase but distance would not as much and the line would get gradually steeper until reached maximum speed
If you stop suddenly how would this look on a distance time graph?
There would be after the increase in distance, a completely straight line and no more increase in distance but increase in time
How can you can you work out the instantaneous speed of an object in a distance time graph?
Find a point in the time in which you want to find the speed, draw a line up from that to the line plotted on the graph and then draw this line parallel to the X axis to the distance. Use the equation speed = distance/ time and do the distance/ time.
why does a Motorbike have more acceleration than a car?
This is because although cars have a higher top speed, motorbikes have a higher acceleration.
Define acceleration
Rate of change of velocity or speed
What are the units for acceleration?
M/s/s or Km/h/s
What is the equation for acceleration (without the V^2 and U^2)?
Acceleration = Final velocity - initial velocity/ time
How do you work out the distance of a velocity time graph?
Find the area that is under the graph
How to calculate acceleration (With V^2 and U^2)
Final velocity^2 - initial velocity^2 = 2 x acceleration x distance
What is Newtons first Law?
When there is no resultant force, the motion of an object is unchanged
What is Newtons first Law?
When there is no resultant force motion of objects in unchanged
What is Newtons Second Law?
Acceleration is directly proportional to force and inversely proportional to mass
What is Newtons third Law?
When forces interact there are 2 forces that are equal in size and opposite in direction
What is the relationship between mass of an object and its acceleration?
The mass increases, the acceleration decreases
