P1 motion Flashcards
Difference between speed and velocity
Speed is a scalar quantity (only has magnitude/size) while velocity is a vector quantity (has both magnitude/size and direction)
Velocity
Describes an object’s direction as well as its speed (vector quantity - has magnitude/size and direction)
Average speed equation
Average speed(m/s)= total distance(m)/total time taken(s)
Acceleration equation
Acceleration(m/s^2) = change in velocity(m/s)/time taken(s)
Distance-time graph y-axis
Distance(m)
Distance-time graph x-axis
Time(s)
Distance-time graph straight line
Constant speed
Distance-time graph horizontal line
Stationary
Speed-time graph y-axis
Speed(m/s)
Speed-time graph x-axis
Time(s)
Speed-time graph horizontal line
Constant speed
Speed-time graph y = 0
Not moving/at rest
Acceleration
Determines a change in speed
Speed-time graph positive gradient
Speed increases with time/acceleration
Speed-time graph negative gradient
Slowing down/deceleration
Area under a speed-time graph
Distance travelled by an object
Free fall
If an object is in freefall, then the object’s weight is the only force acting on it
An object in free fall will…
Accelerate at a constant rate due to gravity
Average value for acceleration on Earth due to gravity
9.82 m/s^2 but usually rounded up to 10 m/s^2
Falling with air resistance
- Objects falling through the Earth’s atmosphere do not continue to accelerate because air resistance slows them down
- The force due to air resistance increases as the speed of a falling object decreases
Air resistance
A frictional force that opposes the motion of objects moving quickly through the air (caused by particles hitting the object)
Weight
The force that acts downwards on an object due to gravity
Distance-time graph in free fall
A line curving upwards
Speed-time graph in free fall
Straight slanted line
Velocity equation
Velocity = displacement/time
Distance
How far an object moves (scalar quantity)
Displacement
The distance an object moved in a straight line from a starting to a finishing point (vector quantity)
Velocity-time graph y-axis
Velocity
Velocity-time graph x-axis
Time(s)
Velocity-time graph horizontal line
Constant velocity
Velocity-time graph y = 0
Not moving/at rest
Velocity-time graph positive gradient
Velocity increases with time/acceleration
Velocity-time graph negative gradient
Slows down/deceleration
Objects that move in a circular path at a constant speed have…
Positive acceleration as their direction is constantly changing (also a change in velocity)
Gradient of velocity-time graph equals to…
Acceleration of the object
Area under velocity-time graph
Distance travelled
Scalar quantity
Only has magnitude(size)
Vector quantity
Has magnitude(size) and direction
Distance-time graph gradient
Speed/velocity
Gradient equation
Rise/run
Vector quantities
- Displacement
- Velocity
- Weight
- Force
- Acceleration
Scalar quantities
- Speed
- Distance
- Temp.
- Time
- Energy
Mass
A measure of the amount of matter an object contains (constant - the same on Earth, the Moon and in space)
Weight
The gravitational force of attraction on an object caused by the presence of a massive second objects (Earth, Moon)
Weight equation
Weight(N) = mass(kg) x gravitational field strength(10N)
Density equation
Density(g/cm^3) = mass/volume
Density
How packed particles are
How to determine the density of an irregularly shaped solid
Method: displacement
- Object submerged fully in liquid
- Volume of water that object displaces is the volume of the objects
- Measure the mass of the object on a balance
- Calculate density using equation
How to determine the density of a regularly shaped objects
- Measure the volume
- Measure the mass using a scale
- Calculate density using equation
How to determine the density of a liquid
- Find mass
- Find volume
- Calculate density using equation
Unbalance forces can change the ___, ___ and ___ of an object
- Direction
- Speed
- Shape
Balanced forces
A pair of forces which are equal in size but opposite in direction
- Stays stationary
- Constant velocity
Unbalanced forces
When the resultant force on each side is not the same
- Acceleration
- Deceleration
- Change in direction
Friction
The force between two surfaces which impedes motion and results in heating
Resultant force
The sum of all forces acting on an object
Newton’s second law
Resultant force(N) = mass(kg) x acceleration(m/s^2)
F = m x a
Extension-load graph y-axis
Force
Extension-load graph x-axis
Extension
Hooke’s law
Force(N) = spring constant x extension
F = kx
Limit of proportionality on extension-load graph
The highest stress at which stress and strain are directly proportional (when the spring can no longer return to its original length when masses are removed)
Moment equation
Moment(Nm) = force(N) x distance from pivot(m)
m = F x d
Moment
The turning effect of a force
A system is in equilibrium when…
There is no resultant force and no resultant turning effect
Centre of mass
The point at which the whole mass of the body is concentrated
Effect of the position of the centre of mass on the stability of simple objects
If the centre of mass is before the pivot then the object will not fall over but if the centre of mass is after the pivot then it will topple over
Pressure equation
Pressure(N/m^2) = force(N)/area(m^2)
P = F/A
