Physics 2a- Motion, Energy and Electricity Flashcards
What is velocity?
Speed in a given direction
What is mass and what is it measure in?
Mass is the amount of matter in an object and it is measured in kg
What is weight and what is it measured in?
weight is a force due to gravity and is measured in Newtons
Does mass and weight ever change?
Mass does not change but weight does.
What is the equation that links weight, mass and gravity?
weight= mass*gravity
A parachuter jumps out of a plane. Describe all of the stages of forces acting upon the parachuter.
1/ When the parachuter jumps out they begin to speed up and the force of weight drags them down.
2/ The air resistance increases and the parachuter slows down slightly, but the weight continues dragging the parachuter down.
3/ The air resistance and the weight become balanced and the parachuter reaches terminal velocity.
4/ The parachuter opens the parachute and the air resistance increases more, this slows down the parachuter.
5/ weight increases and the parachuter descends at a lower speed
What is the resultant force?
The resultant force is the overall force on an object.
If an object has a 0N resultant force can it be moving? can it be accelerating?
If the resultant force of a stationary object is zero, the object will remain stationary.
If there is no resultant force on a moving object it is moving at constant velocity.
What is terminal velocity?
the maximum speed an object can reach
How does a smaller mass affect the acceleration?
a smaller mass= a bigger acceleration
What is thinking distance?
the distance travelled from when the driver reacts to the brakes are applied.
What are the factors affecting thinking distance?
distractions
drugs
alcohol
tiredness
What is braking distance?
is the distance travelled from when the brakes are applied to the car stopping
What are the factors affecting braking distance?
worn out tyres
worn out brakes
icy roads
What is work done?
when a force moves an object through a distance. Energy is transferred and work is done.
How does a car slow down?
Cars have a lot of kinetic energy so to slow them down this kinetic energy needs to be converted into other types of energy.
To stop a car the kinetic energy has to be converted to heat energy as friction between the wheels and the brake pads this causes the temperature of the breaks to increase.
What happens to the energy of falling objects?
falling objects convert their potential energy into kinetic energy The kinetic energy gained= the potential energy lost
Complete this sentence: the extension of a stretched spring is…
The extension of a stretched spring is directionally proportional to the load or force applied.
How do you measure the power output of a person running upstairs?
the energy transferred is the potential energy you gain.
therefore the equation you would use is:
power= massgravityheight/ time
How do you measure the power output of a person accelerating?
The energy transferred is the kinetic energy you gain
therefore the equation you would use is:
power= 1/2massvelocity2/ time
What is the conservation of momentum?
The momentum before is equal to the momentum after
How does a larger force change momentum?
a larger force means a faster change of momentum
What do brakes do?
Brakes reduce the kinetic energy by transferring it into heat energy
What are cars designed to do in a crash?
convert kinetic energy safely. The car slows very quickly so a lot of kinetic energy is converted which could be dangerous, in a crash there is a big change in momentum over very short time.
Cars increase the time over which momentum changes happen, which lessens the forces on the passengers.
Explain features in the car that increase the impact time to prevent injury.
Crumple Zone- the front and back of car crumple on impact as the car body changes shape the kinetic energy is converted. This increases the impact time and decreases the force due to change in momentum.
Side impact bars- strong metal tubes in door panels, direct kinetic energy away from passengers to other areas.
Seat belts- increase the time taken for the wearer to stop
Air bags- slow you down more gradually and prevent you from hitting hard surfaces in car.
What happens when two insulating objects rub against each other?
electrons are scraped off one material and transferred onto the other, leaving a positive static charge on one and a negative static charge on the other.
What is a current?
Current is the flow of electric charges around a circuit, current will only flow if there is a potential difference around the circuit. Current is measured in Amps.
What is potential difference?
The driving force that pushes the current round. Measured in volts
What is resistance?
Anything in the circuit that slows the flow down.
How does resistance affect the current?
The greater the resistance across a component the smaller the current that flows.
Describe what the standard test circuit looks likes and say where all the components go.
The standard test circuit consists of a battery, a variable resistor, a component, a voltmeter and a ammeter.
The ammeter measures current and must be placed in series and never parallel.
The voltmeter measures potential difference and must be placed in parallel around the component.
What is a diode used for?
To regulate the potential different in circuits, it lets current flow freely through it in one direction but not in the other (there is very high resistance in the reverse direction)
Quite useful in various electronic circuits.
what do light emitting diodes (LED’S) do?
LED’s emit light when a current flows through it in the forward direction, they use a much smaller current than other forms of light. They also indicate the presence of a current in a circuit.
What is a light dependent resistor?
An LDR is a resistor that depends on the intensity of light, in bright light the resistance falls and in darkness the resistance is high.
Can be used in automatic street lights
What is a thermistor?
A thermistor is a temperature dependant resistor, in hot conditions the resistance drops and in cool conditions the resistance goes up.
