P2 Flashcards
How do you calculate distance
Speed×time
What are SI units
The agreed set of units used in science
What is a vector quantity
A quantity with both magnitude and direction
What is a scalar quantity
A quantity with magnitude and no direction
What is displacement
The distance from the place you start
What is the difference between speed and velocity
Speed is a scalar quantity, and velocity is a vector quantity
How do multiple (acting together) vector quantities work
If you are given two vector quantities (e.h 2 velocity measurements) you add them together to calculate the total
These quantities will go in a positive direction or negative direction
What is the total velocity of a car traveling to the left at 40mph and a car traveling on the left side of a road, and car traveling on the opposite side of the road at 40mph
They travel in different directions so one is positive and one is negative
-40+40= 0
How are vector quantities shown
We use an arrow to display the direction, and the size of the arrow shows the magnitude
What is acceleration
The change in velocity ÷ change in time
Measured in m/s^2
What does acceleration show
It shows the increase in speed per second.
If something accelerated at 5m/s^2, every second their velocity would increase by 5m/s
How do you use velocities and time to calculate acceleration
Acceleration = (final velocity - initial velocity)÷ time
A = (v-u)÷t
What symbol represents initial velocity
U
What symbol shows final velocity
V
On a distance time graph what does the gradient show
The speed - as distance × time is speed
On a distance time graph what does a horizontal line show
There is no speed - the object is stationary
How do you calculate the gradient
Change in y ÷ change in x
Find two coordinates, subtract the y values and subtract the x values, the divide them
What is the difference between a displacement time graph and a distance time graph
A distance - time graph shows the TOTAL distance travelled, and the gradient is speed
A Displacement - time graph shows how far you have travelled from your original point
It can have a positive or negative gradient
The gradient is velocity
What is a gradient
The degree of steepness on a graph at any point
Also called the slope
What does a velocity time graph show
Acceleration - the gradient
What does a horizontal line mean of a velocity time graph
There is no acceleration, they are moving at a constant speed
How do you calculate distance on a velocity time graph
It is the displacement.
Displacement is the area under the graph
It is calculated by multiplying velocity and speed.
You can find it by working the area out of shapes, then adding them together
On a velocity time graph - how can you tell when something is stationary
If its on the x axis - time increases but there is no velocity
What are SUVAT equations
Equations that can use, displacement, initial velocity, final velocity, acceleration and time to find a missing value (that will be one of the measurements above)
What are the 3 most important SUVAT equations
S= ut+1/2at^2
V^2-u^2 = 2as
V= u+at
What is kinetic energy
The energy associated with a kinetic store
How do you calculate kinetic energy
Ke(J) = 1/2 × mass(KG) × (speed(m/s))^2
Ke = 1/2mv^2
What is Newton’s third law
When body A exerts a force on body B, body B exerts and equal and opposite force on body A
What are non contact forces
A force produced as an object is in a field
The object does not need to be in contact (touching) for the force to act
E.g gravity
How are forces drawn in diagrams
We use a force arrow
As forces are vectors they have magnitude and direction
Ncf arrows’ are drawn from the centre of the object
What are contact forces
The force applied when two objects are in contact ( touching)
E.g pushing a chair
What is an interacting pair
To forces that act upon each other
Examples of contact forces :
Friction - occurs as the atoms that make up two rough surfaces slide over each other
Drag - a force opposite to the direct motion of a body
Upthrust - the force on an object in a fluid dye to a difference in pressure
Tension - solid objects deform slightly when you exert a force on them, and the bonds between the particles are stretched
What does ‘normal’ mean
A force at 90° to the surface of where it hits
A line at 90° to where a wave hits
What is a normal contact force
A contact force that is exerted by a solid surface on an object
Solid objects slightly deform when you exert a force on them, the bonds between particles are compressed
What is the interaction pair on, friction on a sliding box
The force of the box on the surface
The force of the surface on the box
What is a free body diagram
A diagram that shows the forces acting on an object
The object is often represented by a circle and the forces as arrows
What forces do free body diagrams show
ONLY THE FORCES ACTING ON THAT OBJECT
It doesn’t show the forces the object is giving
What is the resultant focre
The total force when two or more forces are added to gather as vectors
(The total strength of the forces acting on an object)
How do you calculate the resultant force, of two forces acting at 90° to each other
Use Pythagoras theorem
A^2+b^2 = c^2
A and be will be the forces that are acting on each other at 90°
What are the forces exerted in a gravitational field
The object on the earth
The earth on the object
What are the forces exerted in a gravitational field
The object on the earth
The earth on the object
What is Newton’s First law of motion
The motion (speed and direction) of an object does not change when the resultant force is not zero
(Law of inertia)
What is inertia
The measure of how difficult it is to change an objects velocity
What is equilibrium
An object is in equilibrium if all the forces cancel - the resultant forces is zero
What is Newton’s second law
F = ma
What happens if the resultant force is not 0
There is motion
What happens to objects that move in a circle
A force is exerted to the center of a circle on an object
The object is constantly changing direction so velocity and acceleration change
What is terminal velocity
The velocity an object reaches when the resultant force is 0
How do you explain the motion of objects when the forces are at an angle
All objects on earth have weight
Ensure all forces have an angle in the opposite direction.
How do you explain the falling momentum of objects
As an object falls it has one force applying to it - gravity
Then it has two forces gravity and drag
Both of these increase until they are at equilibrium
What is momentum
Mass × velocity
What is the law of conservation of momentum
In any interaction or collision momentum before = momentum after
What is elastic collision
A collision in which kinetic energy is conserved
E.g
A moving red ball has an elastic collision with a stationary blue ball, it will stop and the energy is transferred to the blue ballsl
What is an inelastic collision
A collision in which kinetic energy is not conserved
E.g when two snooker balls collide energy is transferred to a thermal store
What is work
The transfer of energy
Done against gravity or friction.
Calculated by multiplying force and distance
How do you calculate work done
Force × distance
Why are joules equal to newton meters
1N = 1kgm/s^2 (force causing 1kg to accelerate at 1m/s^2)
1Nm = 1kgm/s^2 × m
1Nm = 1kgm^2/s^2
What is power
The rate energy is transferred
How do you calculate power
Power = work done ÷ time
What does it mean if a material is plastic
Does not return to its original shape when a force is removed
What does it mean if a material is elastic
A material that returns to its original shape after having a force applied to it
What happens when you stretch a spring
It can return to its original form but has a limit
What is an elastic limit
The furthest distance a spring can return to its original length after having a force applied
What is Hookes Law
Below the elastic limit:
The extension is proportional to the force
How do you calculate the force exerted on a spring
Constant × extension
F = k×m
What does the spring constant tell you
How easy or hard it is to stretch a spring
How do you calculate energy transferred in stretching
Similar to kinetic energy equation
1/2 contant ÷extension^2
1/2 kx^2
What is the extension of a spring
Its increase in size from an original length
What happens when you stretch other materials like an elastic band
There is a non linear relationship between force and extension
The extension increases differently each time when the force increases
As they are elastic they return to their original position
How do some materials return to their original shape (e.g tennis rackets)
All objects store energy when they deform
Scientists developed materials that transfer the energy back when they regain their shape
What is a gravitational field
A region where mass experiences an attractive force
How to calculate the gravity force (weight)
Mass × gravitational field strength
What is the gravity constant
Another term for gravitational field strength
What increases the size of a force in a gravitational field
The mass of an object or the field is greater
The distance between the object and field is smaller
What is weight
Weight is what we call the force of the Earth on an object
It is equal to mass × gravitational field strength
What is the gfs on earth
10N/Kg
What is acceleration due to gravity
It is normally taken as 10m/s^2
(9.8m/s^2)
How do you calculate the size of a resultat force in a gravitational field
Mass × acceleration due to gravity
What is gravitational potential energy
The energy transferred to the gravity store when you lift a box in a gravitational field
How do you calculate gravitational potential energy
Mass × height × gravitational field strength
What is a pivot
The point at which a force produces a turning effect
What is a moment
The turning effect of a force
Is it easier or harder to produce a turing force close or further away to an object
Futher away
How do you calculate the moment of a force
Force × distance
Moment is measured in Nm
What is the principle of moments
An object is balanced if the clockwise and anticlockwise moments are equal
What is a lever
A rod (or other) that wont bend with a pivot
A force applied at one end produces a force in the opposite direction at the other end
It is used to produce rotational forces
What is a force multiplier
A factor that increases the effectiveness of a force
What is effort (levers)
The force you exert on a lever
What is load
The force the lever exerts on the loasb
How does the distance of the pivot and load effect the effort needed
The closer the pivot to the load the smaller the effort needed
What is mechanical advantage
The ratio of effort to load
How do you calculate mechanical advantage
Load ÷ effort
How do gears transmit forces
The ratio of the diameter of each cog tells you the ratio of effort to load
Cogs can be used to change direction of a rotating force, or the speed it acts at
How does the number of teeth on a cog effect its rotations per minute
The less teeth it has the smaller its diameter
So more rotations are made per minute
How does pressure in a fluid cause a force
It produces a force 90° to any surface
Pressure acts from all sides not just abobe
What is the equation for pressure
Pressure = force normal to the surface ÷ area
What is a hydraulic machine
A machine that uses liquid to transmit a force
How do simple hydraulic machines work
A piston (similar to a syringe) has a small force exerted on it, causing the area to decrease
This decrease of area increases the pressure of another.
This is transmitted to the other end and the pressure increase causes a larger force to be exerted
The pressure throughout the whole system is the same at any given time
The second piston has a greater surface area - allowing for a greater force
How do you calculate momentum
P = mv
Momentum is in kgm/s
How do you calculate force from momentum
Force = ∆p ÷ t
