Dynamics Flashcards
Scaler quantity
Fully describes by a magnitude
Vector quantity
Fully describes by magnitude and direction
Examples of scaler quantitities
Speed
Distance
Time
Energy
Examples of vector quantities
Force
Velocity
Displacement
Acceleration
Average speed
Total distance divided by total time
Instantaneous speed
The speed at a point in time
Experiment to measure average speed
Measure the distance between 2 points with an appropriate measuring devise
Start timer as object passes point A
Stop timer as it passes through point B
Experiment to measure insataneous speed
A small length of a card is attached to a car
The car passes through a light gate
The timer measure how long it takes the card to pass through the light gate
Experiment to measure acceleration
Setup the software to calculate the initial speed at the first light gate and the final speed at the second light gate.
Release the trolley from rest so that it passes through the two light
gates.
Record the time taken for the trolley to pass from the first to the second light gate, using the stopclock.
What does constant speed require
Balanced forces
When does turminal velocity occur
Resistive forces balance the driving force
Newton’s first raw
An object will remain at rest or travel at the same speed, in a straight line, unless an unbalanced force acts on the object.
Newton’s second law
An object will accelerate in the same direction as the unbalanced force acting on it.
Force and acceleration are directly proportional
Newton’s third law
If A exerts a force on B, B exerts and equal but opposite force on A
Horizontal motion
Once the projectile has been fired there are no horizontal forces acting on it, therefore the horizontal velocity is constant.
Falls at a constant speed
Vertical motion
The vertical motion can be described as having constant vertical acceleration.
Affected by gravity
Displacement
Distance between 2 points in a given direction
Acceleration
The change in unit time
Friction
A force that oppose the balance of an object
Terminal velocity
The constant velocity reached by an objects free fall
Why would instantaneous speed have higher results than average speed
Instantaneous speed is calculated at max velocity
Forces can change
Shape
Speed
Direction of object
Questions of the weight of objects and people on the moon
Gravitational Reid strength numerically is equal to the accerlaeration when frictional forces are ignored
Friction on lorry vs car
Larry has a higher weight, which means there is more friction acting on it when it turns, lorry weals are designed to keep lorry on the road
Friction on skier
Skier need a low friction, This is why they wax their boards
Why are to forces acting on an object not cancel each other out
They act on the same object
Equal and opposite forces cancel each other out
What is acceleration when frictional forces are negligable
9.8ms-2
Sky diver
Weight is more than air resistance
Terminal velocity- meaning weight and resistance balance falling at a constant speed
Parachute goes up meaning there is more air resistance than weight
Blanked forces act on skydivers
Force on satalight
Forces on a satalight are unbalance as satalight changes direction
Feather and hammer dropped on the moon from same height
They hit surface at the same time
Moon has no atmosphere meaning ther is no air resistance
Calculation of light year
3x108 x 60 x 24 x24 x 365.25
If it is slowing down
Negative acceleration
Efficiency
How much useful energy is transferred and how much is lost
Pendulum
The larger tha mass the more poetail energy
Mass has potential energy
Starts with potential energy and converts into kinetic energy
The pattern continues
Does not have enough energy to reach original height
Et = Ek + Ep
The hier the mass
The lower the acceleration
The higher the force
The higher the accleration
Forces on a ball
Ball excess coward force on racket
Racket Eckerts and equal but opposite force on ball
Object going round earth
The greater the velocity, the greater the distance
When it is fired at the right vertical velocity will go around to earth
Downwards motion matches curvature of earth
Friction less environment
Object will orbit earth eg a satalte
Vacuum flask
Stop- Stops evaporation
Silver - prevents radiation
Vacuum - no conduction
Less dense
Away from normal
Accleration from v-t graph
Gradient
