Motion and Forces

Question 1

What is a vector?

Answer 1

A quantity with a magnitude and a direction e.g. Force, lift, thrust, velocity, displacement

Question 2

What is a scalar?

Answer 2

A quantity with only a magnitude e.g. Length, mass, area, volume, speed, work

Question 3

What us displacement?

Answer 3

The straight line distance from start to finish

Question 4

What is velocity?

Answer 4

Speed in a direction

Question 5

What is the equation for velocity?

Answer 5

Displacement / time

Question 6

What does the gradient represent on a distance-time graph?

Answer 6

Speed. When it is flat, speed is 0. It can be calculated by change in y / change in x or with a tangent.

Question 7

What is the equation for speed?

Answer 7

Speed = distance / time

Question 8

What does the area under the line represent on a velocity-time graph?

Answer 8

Distance travelled

Question 9

What is the equation for final velocity?

Answer 9

Final velocity^2 - Initial velocity^2 =2accelerationdisplacement
V^2 - u^2 = 2as

Question 10

What is mass (m)?

Answer 10

The amount of matter in something
Measured in kg
Does not change

Question 11

What is weight (W)?

Answer 11

The force acting on a mass due to gravity
Measured in N
Changes when gravity changes

Question 12

What is gravity (g)?

Answer 12

An acceleration due to gravitational attraction of a force
Measured in m/s^2 or N/kg
Depends on size of the big mass and distance from it
Has a value of 10m/s^2 on Earth

Question 13

What are the equations for force and weight?

Answer 13

Force = mass * acceleration
F = ma
Weight = mass * gravity
W = mg

Question 14

What are Newton’s three laws?

Answer 14

1. An object will not move or move at a constant velocity unless acted on by an external force
2. F = ma
3. Every action has an equal and opposite reaction

Question 15

What is circular motion?

Answer 15

When an object is moving in a circle it is travelling at 90 degrees to the force of tension. Its velocity is 90 degrees to it. Centripetal force is in the same direction to tension, pulling it in. For circular motion to occur there must be a centripetal force at 90 degrees to the tangential velocity.

Question 16

What is centripetal force?

Answer 16

The force towards the centre in a circular motion

Question 17

What is conservation of motion?

Answer 17

In a closed system momentum must be conserved. This means that the total momentum before is the same as the total momentum after an event. As p1 = p2, mv1 = mv2, so you can work out resultant velocity or the second object’s mass if given enough information.

Question 18

What is the formula for momentum?

Answer 18

Momentum = mass x velocity
P = mv
kgm/s = kg * m/s

Question 19

What is the formula for work done?

Answer 19

Work done = force x distance in direction of force
W = Fd
J = N * m

Question 20

What is power?

Answer 20

How quickly energy is transferred

Question 21

What is the equation for power?

Answer 21

Power = energy transferred / time
Watt = joules / seconds

Question 22

What is the equation for kinetic energy?

Answer 22

Kinetic energy = 1/2 x mass x velocity^2

KE = 1/2mv^2

Question 23

What is the equation for distance?

Answer 23

Distance = (1/2 x mass x velocity^2) / force (from the breaks)
D = (1/2mv^2)/F

Question 24

What is the equation for force with mass, velocity and time?

Answer 24

Force = (mass x change in velocity) / time
F = (m*v-u)/t
OR
Force = Change in momentum / time
F = (mv - mu)/t

Question 25

What are some car safety features?

Answer 25

Airbags
Crumple zones
Seatbelt

Question 26

How do car safety features work?

Answer 26

They increase the time in a collision, reducing the force.

Question 27

What is an impulse?

Answer 27

Change in momentum, or force x time. Its units are Ns or Mm

Question 28

What is the equation for acceleration?

Answer 28

Acceleration = Change in velocity / time
a = (v-u)/t

Question 29

How can you investigate the motion of a trolley on a ramp?

Answer 29

Put a trolley with a card on onto a ramp. Put two light gates on the ramp, so that the trolley will disrupt them when passing. Adjust the height of the ramp until the trolley just begins to move. The light gates will record the speed and time, so acceleration can be worked out. Attach the trolley to a hanging mass by a string and repeat with different masses.

Question 30

What is inertia?

Answer 30

The tendency for motion to remain unchanged. Unless acted on by a resultant force, an object will stay at rest or at a constant velocity. An object’s inertial mass measures how difficult it is to change the velocity of an object (m=F/a)

Question 31

What is the equation for stopping distance?

Answer 31

Stopping distance = Thinking distance + Braking distance

Question 32

What factors affect thinking distance?

Answer 32

Reaction time: includes tiredness, alcohol, drugs, and distractions
Speed

Question 33

What factors affect braking distance?

Answer 33

Speed
Mass of the car
Condition of the breaks
Friction between tyres and road

Question 34

How can you measure someone’s reaction time?

Answer 34

Use the ruler drop test:
Rest your arm on the edge of a table. Get someone to hold a ruler at the top of your hand and drop it. The further it fell, the longer the reaction time.

Question 35

What is the average mass of a car, a single decker bus, and a loaded lorry?

Answer 35

Car: ~1000kg
Single decker bus: ~10,000kg
Loaded lorry: ~30,000kg