Physics 2a- Motion, Energy and Electricity

Question 1

What is velocity?

Answer 1

Speed in a given direction

Question 2

What is mass and what is it measure in?

Answer 2

Mass is the amount of matter in an object and it is measured in kg

Question 3

What is weight and what is it measured in?

Answer 3

weight is a force due to gravity and is measured in Newtons

Question 4

Does mass and weight ever change?

Answer 4

Mass does not change but weight does.

Question 5

What is the equation that links weight, mass and gravity?

Answer 5

weight= mass*gravity

Question 6

A parachuter jumps out of a plane. Describe all of the stages of forces acting upon the parachuter.

Answer 6

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

Question 7

What is the resultant force?

Answer 7

The resultant force is the overall force on an object.

Question 8

If an object has a 0N resultant force can it be moving? can it be accelerating?

Answer 8

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.

Question 9

What is terminal velocity?

Answer 9

the maximum speed an object can reach

Question 10

How does a smaller mass affect the acceleration?

Answer 10

a smaller mass= a bigger acceleration

Question 11

What is thinking distance?

Answer 11

the distance travelled from when the driver reacts to the brakes are applied.

Question 12

What are the factors affecting thinking distance?

Answer 12

distractions
drugs
alcohol
tiredness

Question 13

What is braking distance?

Answer 13

is the distance travelled from when the brakes are applied to the car stopping

Question 14

What are the factors affecting braking distance?

Answer 14

worn out tyres
worn out brakes
icy roads

Question 15

What is work done?

Answer 15

when a force moves an object through a distance. Energy is transferred and work is done.

Question 16

How does a car slow down?

Answer 16

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.

Question 17

What happens to the energy of falling objects?

Answer 17

falling objects convert their potential energy into kinetic energy The kinetic energy gained= the potential energy lost

Question 18

Complete this sentence: the extension of a stretched spring is…

Answer 18

The extension of a stretched spring is directionally proportional to the load or force applied.

Question 19

How do you measure the power output of a person running upstairs?

Answer 19

the energy transferred is the potential energy you gain.
therefore the equation you would use is:
power= massgravityheight/ time

Question 20

How do you measure the power output of a person accelerating?

Answer 20

The energy transferred is the kinetic energy you gain
therefore the equation you would use is:
power= 1/2massvelocity2/ time

Question 21

What is the conservation of momentum?

Answer 21

The momentum before is equal to the momentum after

Question 22

How does a larger force change momentum?

Answer 22

a larger force means a faster change of momentum

Question 23

What do brakes do?

Answer 23

Brakes reduce the kinetic energy by transferring it into heat energy

Question 24

What are cars designed to do in a crash?

Answer 24

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.

Question 25

Explain features in the car that increase the impact time to prevent injury.

Answer 25

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.

Question 26

What happens when two insulating objects rub against each other?

Answer 26

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.

Question 27

What is a current?

Answer 27

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.

Question 28

What is potential difference?

Answer 28

The driving force that pushes the current round. Measured in volts

Question 29

What is resistance?

Answer 29

Anything in the circuit that slows the flow down.

Question 30

How does resistance affect the current?

Answer 30

The greater the resistance across a component the smaller the current that flows.

Question 31

Describe what the standard test circuit looks likes and say where all the components go.

Answer 31

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.

Question 32

What is a diode used for?

Answer 32

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.

Question 33

what do light emitting diodes (LED’S) do?

Answer 33

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.

Question 34

What is a light dependent resistor?

Answer 34

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

Question 35

What is a thermistor?

Answer 35

A thermistor is a temperature dependant resistor, in hot conditions the resistance drops and in cool conditions the resistance goes up.