GCSE Unit 2(i) (and static electricity)

Question 1

Speed and velocity definitions

Answer 1

Speed - how fast you’re going
Velocity - how fast you’re going in a specified direction

e.g. mph, m/s etc.

Question 2

Acceleration definition

Answer 2

How quickly the velocity is changing, measured in m/s2

Question 3

Characteristics of a d-t graph

Answer 3

Gradient = speed
Flat sections = stationary
Steeper gradient = faster speed
Downhill sections = going back towards starting point
Steepening curve = acceleration
Levelling off curve = deceleration

Question 4

Characteristics of v-t graphs

Answer 4

Gradient = acceleration
Flat sections = steady speed
Steeper gradient = greater acceleration/deceleration
Uphill sections (/) = acceleration
Downhill sections (\) = deceleration
Area under any section = distance travelled in the time interval
Curve = changing acceleration

Question 5

Speed, distance, time formula

Answer 5

Speed = distance / time

Question 6

How do you find speed in a d-t graph?

Answer 6

Vertical / horizontal

Question 7

How do you find acceleration in a v-t graph?

Answer 7

Vertical / horizontal

Question 8

Definition of weight.

Answer 8

The strength of force pulling down on an object - the pull of gravity. (N)

Question 9

Definition of mass.

Answer 9

How much stuff an object has in it. (Kg)

Question 10

What is the first law of motion?

Answer 10

Balanced forces mean no change in velocity.

Question 11

What is the second law of motion?

Answer 11

A resultant force means acceleration, the object will accelerate towards the bigger force.

Question 12

What is the third law of motion?

Answer 12

If object A exerts a force of object B then object B will exert the same amount of force on object A.

Question 13

What is drag or friction?

Answer 13

Drag acts in the opposite direction to movement. The higher the speed, the more drag there is.

Question 14

What is terminal velocity?

Answer 14

When the opposite forces balance. An object with a small surface area will have a higher terminal velocity.

Question 15

What is the stopping distance?

Answer 15

Thinking distance (constant speed) + braking distance (decelerating to a stop)

Question 16

What affects the thinking distance?

Answer 16

Speed, tiredness, drugs, alcohol, old age, distractions, visibility

Question 17

What affects braking distance?

Answer 17

Speed, how heavily loaded the vehicle is, quality of brakes, grip (road surface, weather, tyre quality)

Question 18

What is work done?

Answer 18

When a force moves an object, energy is transferred and work is done.

Question 19

Formula for work done

Answer 19

Work done = force x distance

Question 20

What is kinetic energy?

Answer 20

Objects have kinetic energy when they’re moving. An object moving faster will have more kinetic energy than one moving slower. Measure in J.

Question 21

Kinetic energy formula

Answer 21

Kinetic energy (J) = 1/2 x mass (g) x velocity^2 (m/s)

Question 22

What is gravitational potential energy?

Answer 22

When you push something up, you do work against the force of gravity. The force pulling down on an object is called weight.

Question 23

Formula for gravitational potential energy

Answer 23

GPE gained = mass (kg) x strength of gravity (10N on Earth) x height change (m)

Question 24

What is elastic potential energy?

Answer 24

Energy stored when work is done against an object to change its shape. Springs store this when they’re compressed or stretched.

Question 25

Momentum formula

Answer 25

Momentum (kg m/s) = mass (kg) x velocity (m/s)

Question 26

Momentum before and after

Answer 26

Momentum is conserved when no external forces act, so the total momentum is the same as it was before.

Question 27

Force acting formula

Answer 27

Force acting (N) = Change in momentum (kg m/s) / Time taken for change to happen (s)

Question 28

What do crumple zones, seat belts and air bags in cars help with in a crash?

Answer 28

Crumple zones - crumple on impact, increasing the time taken for the car to stop.
Seat belts - stretch slightly, increase the time taken for wearer to stop. This reduces the force acting on chest.
Air bags - slow you down more gradually.

A sudden change in momentum means that the force on the body will be very large and you will be more likely to sustain an injury.

Question 29

How is static built up?

Answer 29

When two insulating materials are built together, electrons with be scraped off one and dumped on the other. The object with the gained electrons will have a negative charge. One object will have a positive static charge and one will have a negative static charge. Like charges repel, opposite charges attract.