Unit 2A - Motion, Energy And Electricity Flashcards
On a distance time graph what does the gradient represent?
Speed
What’s the difference between speed and velocity?
Speed - how’re fast you are going with no regard to direction
Velocity - how fast you are going with a specified direction
On a distance-time graph what are acceleration and deceleration shown by?
Curves
If you are stationary what is this shown as on a distance-time graph?
Flat line
How do you calculate speed from distance time graphs?
Speed = gradient = y/x
What is acceleration?
Acceleration is how quickly velocity is changing
What is the formula for acceleration?
Acceleration = Change in velocity / Time
A car accelerates from 2m/s to 6m/s in 5.6s. What it’s acceleration?
0.71m/s^2
In a velocity-time graph what does the gradient represent?
Acceleration
What do flat sections represent on velocity-time graphs?
Steady speed
What is acceleration shown by in velocity-time graphs?
Straight uphill line
What does the area under a velocity-time graph represent?
Distance travelled
What does a curve means in a velocity-time graph?
Changing acceleration
What is gravitational force?
Gravitational force is the force of attraction between all masses
Are weight and mass the same?
No
What is the difference between mass and weight?
Mass is the amount of “stuff” in an object where as weight is caused by the pull of gravitational force.
Between the earth and the moon will the mass and weight be the same?
The mass will stay the same however the weight will change because there is less or more gravitational force
What is the formula for weight?
Weight = mass x gravitational field strength
What is the gravitational field strength one earth?
10N/kg
What is the resultant force?
Resultant force is the overall force on a point or object
If there is a resultant force acting on an object what will it change?
A resultant force will change the velocity
On a car there is a driving force of 1000N and air resistance of 600N , what is the resultant force?
400N to the left, causing an acceleration
If there is is no resultant force on a stationary object what will happen?
The object will remain stationary
If there is no resultant force in a moving object what will happen?
The moving object will carry on moving at a constant velocity
Is there a non-zero resultant force on a object what happens?
The object will accelerate in the direction of the force
What is the formula for resultant force?
F = MA
F being the resultant force
Is a reaction force equal or different?
Equal
What is the definition of a reaction force?
When two objects interact, the force they exert on each other are equal and opposite, this is called a reaction force
If you push something does it push you back just as hard or not as hard?
Just as hard
What is the two other name for friction and where do they apply?
Fluids (air or liquids) - drag and resistance
What does friction do?
Slow things down
What is terminal velocity?
Terminal velocity is the maximum speed an object can reach
Why does an object reach terminal velocity?
When an object first sets off falling the force of gravity is a lot higher than the force of friction, this causes the object to accelerate. As the speed increases the causes the friction to build up, and gradually reduce the acceleration. Eventually the friction force and the accelerating force is equal and the object won’t accelerate any more, it has reached its maximum velocity
Terminal velocity of falling objects is due to?
Their shape and area
Would you want a higher or lower terminal velocity if you were a skydiver? And how would you do this?
You would need a lower terminal velocity to make it safer you can do this by using a parachute which increases the area meaning there is more drag slowing you down
What is stopping distance the sum of?
Stopping distance is the sum of the thinking distance and breaking distance?
What is the distance the vehicle travels during the drivers reaction time called?
Thinking distance
What is breaking distance?
The distance the car travels under the breaking force
What are the two main factors that affect thinking distance?
How fast you’re going, how dopey you are
What are the four main factors affecting braking distance?
How fast you’re going, how good your brakes are, how good your tyres are, how good your grip is
What are the other two factors that are a major factor in accidents?
Bad visibility - rain
Distractions - radio
What is the definition of work done?
When a force moves an object through a distance energy is transferred and work is done
What is the formula for work done?
Work done = force x distance
What’s another word for work done ?
Energy transferred
Is a tyre is dragged 5m over the grass, the total pulling force is 340N, what is the work done?
1700J
What is gravitational potential energy?
Gravitational potential energy is the energy that an object has because of its vertical position in a gravitational field
What is the formula for gravitational potential energy?
Gravitational potential energy = mass x gravitational field strength x height
What is kinetic energy?
The energy of movement
What’s the formula for kinetic energy?
Kinetic energy = 1/2 x mass x speed^2
The more it weighs and the faster it is going, the bigger or smaller the kinetic energy?
Bigger
Kinetic energy transferred is also called?
Work done
When a car is braking what does kinetic energy transferred equal?
Work done by brakes
When an object is falling what converts to form kinetic energy?
Potential energy
When an object is falling potential energy gained equals ?
Potential energy lost
Why do meteors usually burn up before they reach the earth?
When falling towards the earth the potential energy is converted into kinetic energy. Some of this kinetic energy is converted to heat and sound because of the friction due to the collisions with particles. The temperature become so extreme that the meteors burn up.
If work is done to an elastic object what is it stored as?
Elastic potential energy
What is an elastic object?
Any object that you can stretch and after the force is removed it goes back to its original shape
When the force is removed what is the elastic potential energy converted into?
Kinetic energy as it returns to its original shape
Extension is directly proportional to the?
Force
What’s the symbol equation for force relating to extension?
F = k x e (k is the strings constant)
What’s the letter that means the springs constant?
K
Does the extension and force always extend proportionality?
No there is a maximum force that the elastic object can extend, after this point the graph levels of
What is the limit of extension called?
Limit of proportionality
What happens if you increase the force past the limit of proportionality?
The material will be permanently stretched and not return to its original shape when the force is removed
What is power?
The rate of doing work
Is power the same as force and energy?
No
What is the formula for power?
Power = work done / time
What is power measured in?
SWatts
What is one watt the same as?
1 joule of energy transferred per second
If you go upstairs what is the energy transferred?
Potential energy gained
If you are accelerating energy transfered is to?
Kinetic energy
You you have gained potential energy then the formula for power is?
Power = mgh / time
What is the formula for momentum?
Momentum = mass x velocity
What letter do you use to represent momentum?
P
The momentum before is different to the momentum after?
No the momentum before = the momentum after
If a force acts on a object what does it cause?
A change in momentum
If a momentum changes very quickly for forces will be?
Very large
What is the effect of large forces on the body?
Injury
How does a car charge the force applied on you in a crash?
Slows you down over a longer time, takes linger for a change in momentum and so a smaller force
How to brakes reduce the kinetic energy of a car?
They convert it to heat and sound energy
How do regenerative brakes work?
They use the main system that drives the car to do the braking. The braking puts the vehicles engine in reverse slowing down the wheels. This motor acts as an electric generator converting the kinetic energy into electrical energy to be used later instead of wasting it as heat.
What are the four ways that cars are designed to make them safer?
Crumple zones, side impact bar, seat belts and air bags
What are crumple zones?
Areas at the front and back of the car that crumple up on impact
How do crumple zones reduce impact?
The cars kinetic is converted into other forms when the cars body is changed shape increasing the impact time, decreasing the force
What are side impact bars and what do they do?
They are strong metal tubes inside the car door panels that direct the kinetic energy of the crash away from the passenger to areas like the crumple zones
How do air bags increase impact time?
They slow you down more gradually and prevent you from hitting your head
How do seat belts reduce the forces in the crash?
They stretch slightly increasing the time taken for the wearer to stop, reducing the forces acting on the chest, some kinetic energy is absorbed by this stretching
What determines how powerful a car is?
The size and design
Why are cars designed to be aerodynamic?
Reduces air resistance, increasing the top speed
What is static energy?
Charges which are not free to move
A build up of static is caused by?
Friction
How is static electricity formed between objects?
When two insulating materials are rubbed together, negatively charged electrons will move off one and go onto the other
If it loses an electron it will have which charge?
Positive
What happens when you rub a cloth with a polythene rod?
Electrons move to it, giving it a negative charge
What is the name of the rod which when you rub it with a cloth electrons move from it giving it a positive charge?
Acetate
If electrical charges can move well through a material, the material is called a?
Conductor
What are the positive and negative charges called?
Electrostatic forces
What is current?
The rate of flow of charge
What is measured in Amps?
Current
What is potential difference?
The driving force that pushes the current around, the work done per coulomb of charge
Potential difference is the same as?
Voltage
What is resistance?
Anything in a circuit that slows the flow down
What is potential difference measured in?
Volts
What is resistance measured in?
Ohms
What is charge measured in?
Coulombs
More charge causes a bigger or smaller current?
Bigger
What is the formula relating current and charge?
Current = charge / time
What is the formula relating potential difference and charge?
Potential difference = work done / charge
What components measure volts and amps?
Ammeter and a voltmeter
What shape of graph represents these three potential difference - current graphs?
Different resistors
Filament Lamp
Diode
Straight line, slope
Curve like x^3
Curving upwards after x = 0
Why does the current only flow in one direction through a diode?
There is high resistance in the opposite direction
A higher temperature causes a higher?
Resistance
Why does resistance increase with temperature?
Some electrical charge that flows through a resistor is transferred to heat energy. This causes the ions in the conductor to vibrate more, making it more difficult fir the charge-carrying electrons to get through
Why is there a limit to the amount if current that can flow through a resistor?
Increase in current means an increase in temperature, which means an increase in resistance decreasing the current meaning it levels off and can’t increase anymore
What’s the formula for current, potential different and resistance?
Potential difference = current x resistance
How does the current flow through a diode?
In one direction
What does LED stand for ?
Light - emitting diode
What are LED’s?
A device that emits lights when the current is flowing in the forward direction
What type of light is used for digital clocks, traffic lights and remote controls ?
LED
What does LDR stand for?
Light - dependant resistor
What is a LDR?
It is a resistor that depends on the intensity of the light, bright light the resistance falls, in darkness the resistance is highest
What are LDR ‘s used for?
Outdoor light and automatic night lights
What is a thermistor?
A temperature dependant resistor, hot conditions the resistance drops and in cool conditions the resistance goes up
What is a series circuit?
A circuit when all the components are connected in a line
What is a parallel circuit?
A circuit in which each component is separately connected to the supply
In which circuit parallel or series does the circuit stop if you remove one component?
Series
The potential difference is shared in which circuit?
Series
In a series circuit the current is?
The same everywhere
In a series circuit the resistance?
Adds up
In a parallel circuit is the potential difference the same or different across the components?
Same
The current is shared in which circuit ?
Parallel
In everyday life what is an example of a series circuit?
Christmas lights bulbs can have very small voltage and it is shared out between them
Example of something with a parallel circuit?
Car
Two advantages of using a parallel circuit?
Everything can be turned on separately and everything gets the full voltage of the battery
