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Physics 1) Forces and Motion - Coggle Diagram
Physics
1) Forces and Motion
Formulas
Average Speed = distance moved / time
Acceleration = Change in Velocity / Time
V^2 = U^2 +2as
Moment = mass x perpendicular distance between line of action and pivot
mass = weight x gravitational field strength
momentum = mass x velocity
Force = mass x acceleration
Stopping distance = thinking distance + braking distance
Force = Spring constant x extension
Force = change in momentum / time taken
Resultant force = Mass x Acceleration
2) Acceleration
Acceleration means how quickly the velocity is changing
Acceleration
= Change in Velocity / Time Taken.
It is measured in m/s^2
V^2 = u^2 + 2as
v = final velocity
u = initial velocity
s = distance
a = acceleration
8) newtons 3 laws of motion
First law -- Balanced forces mean no change in velocity
When a moving vehicle is moving at a constant velocity then the forces on it must be balanced. To keep going at a steady speed, there must be zero resultant force.
Second law -- A resultant force means acceleration
The overall unbalanced force is often called the resultant force
An unbalanced force will always produce acceleration or deceleration on a force diagram , the arrows will be unequal
Five types of acceleration:
1) starting
2) stopping'
3) speeding up
4) slowing down
5) changing direction
Force is measured by the formula:
Force = Mass x Acceleration
F = force (N)
m = mass (Kg)
a = acceleration (M/s)
Third law -- Reaction forces:
If object A exerts a force on object B, then object B exerts an equal and opposite force on object A
That means that if you push an object, the object will push back against you, just as hard
1) Speed and Velocity
Speed
is how fast an object is moving with no regard to the direction.
Velocity
is how fast an object is moving with regard to the direction
Average speed
= distance moved / time taken
3) Distance-Time Graph
Key Learning from this graph are:
1) The gradient(slope) at any point gives the speed.
2) Flat sections are where it's stopped
3) A steeper graph means it's going faster
4) Curves means acceleration
5) A curve getting steeper means its speeding
6) A curve going down means its slowing down
Distance-Time graphs tell you how fast an object is moving and how far it's travelled.
x-axis = time / s
y-axis = distance / m
4) Velocity-Time Graphs
Velocity-Time Graphs shows us how the velocity of an object changes over time.
Key learning from this graph are:
1) gradient = acceleration
2) Flat sections means steady speed
3) The Steeper the graph, the greater the acceleration or deceleration
4) uphill sections are acceleration
5) downhill sections are deceleration
6) the area under any part of the graph = the distance
travelled in that time interval
7) a curve means changing acceleration
5) Mass, Weight and Gravity
Gravity
is the Force of attraction between all masses. All masses have gravity but we can notice it only when the masses are really big like planets
Mass
is the amount of 'stuff' in an object and it stay the same anywhere in the universe. Weight is caused by gravity
An object has the same mass whether it's on the Earth or on the moon --- but its weight will be different. This is because the moon's gravitational pull is weaker than the earth's gravitational pull, so the weight will be less
Weight
= Mass x gravitational field strength
w = weight
m = mass
g = gravitational field strength
Weight is measured in newtons(N)
6) Forces
Forces acting on a body
There are 4 forces acting on a object at all times:
Thrust, Drag, Weight, Reaction
Force is simply a push or pull. There are 7 types of forces. Force is measured in Newtons
1) Gravity or weight = close to a planet this acts straight downwards
2) Reaction force - acts perpendicular to a surface and away from it
3) Electrostatic force between two charged objects. The direction depends on the type of charge. Ex Magnets
4) Thrust --- push or pull due to an engine or rocket speeding something up
5) Drag or air resistance or friction which is slowing the thing down
6) Lift -- due to an airplane wing
7) Tension in a rope or cable
7) Friction
Friction is there to slow things down. There are 3 types of friction:
a) Static friction - it is the friction between solid surfaces which are gripping
b) Sliding friction - frictions between solid surfaces which are sliding past each other
c) Resistance or drag
To reduce sliding friction, we use lubricants
The denser the material, the higher the drag is -- a car moving underwater experiences more drag compared to a car moving on land.
To increase drag, you need to increase the surface area. e.g. a person jumping with a parachute. The surface area increases as the parachute opens up, therefore increasing drag and slowing them down.
9) Combining forces
Vectors quantities have size
AND
direction
e.g. force, velocity, acceleration, momentum, etc.
Scalar quantities only have size and no regard to direction:
e.g. mass, temperature, time, length, etc.
To work out resultant force, you need to combine vectors.
e.g.220N north, 180N south and 90N south. The resultant force is in the south by 50N(180 + 90 = 270)(220-270 = -50)
10) Terminal Velocity
Moving objects can reach a terminal velocity:
when an object first starts to fall, it has much more force accelerating on it than resistance slowing it down. As its velocity increases, the resistance builds up. When the resistance = accelerating force, then the object has reached terminal velocity.
The shape and area affect the terminal velocity of falling objects. The accelerating force on all objects is gravity and it would make them all accelerate at the same rate, if it wasn't for air resistance. e.g A man jumping with a parachute has a higher area slowing his speed Vs jumping without a parachute
11) Stopping distance
Stopping Distance is the distance covered in the time between the driver first spotting a hazard and the car coming to a complete stop. It is measured by the formula:
Stopping Distance = Thinking Distance + Braking Distance
Thinking Distance
is = The distance the car travels in the time between the driver noticing the hazard and applying the brakes. It is affected by two main factors: a) How fast you're going b) Your reaction time - This can be affected by tiredness, drugs, alcohol and old age.
Braking Distance
is The distance the car travels during its deceleration whilst the brakes are being applied. It is affected by four main factors:
a) How fast you're going
b) The mass of the vehicle
c) How good the brakes are
d) How good the grip is - this depends on three things: road surface, weather conditions and the tires
Thinking Distance is around 30%. Eg. if speed is 30mph, then thinking distance is 9m
12) Momentum and collisions
Momentum (Kg m/s) = Mass x Velocity:
The greater the mass of an object and the greater its velocity, the more momentum the object has
Initial momentum = Final momentum
Momentum is conserved when no external forces act
Forces cause changes in momentum
Force (N) = change in momentum / time
N = (mv - mu)/t
When the momentum rapidly changes, its force can be reduced by increasing Time. Eg Airbags increase time taken from a accident thus reducing the force
13) Turning effects
A moment is the turning effect of a force
Moment = Force x Perpendicular distance between line of action and pivot
Moment is measured in Nm (newton Meters)
When forces act around a fixed point called a pivot, they have turning effects called moments
14) Centre of gravity
The weight of an object can be thought to act through a point called its Centre of gravity
The centre of gravity hangs below the point of suspension
Center of Gravity can be found by:
15) principle of moments
Forces are not always equal across all supports
The closer you are to the force, the more work you are doing
If the total anticlockwise moments do not equal the total clockwise moments, there will be a resultant moment
16) Hooke's Law
Hooke's law says that extension is proportional to Force
Applying a force to an object can cause it to change shape temporarily... or even permanently
Hooke's law stops working when the force is great enough
A material can return to its original shape after an elastic deformation
