Topic 5

Question 1

Upthrust

Answer 1

Resultant force upwards when greater pressure at bottom of object compared to top when submerged in a fluid

Question 2

Typical walking speed

Answer 2

1.5 m/s

Question 3

Typical running speed

Answer 3

3 m/s

Question 4

Typical cycling speed

Answer 4

6 m/s

Question 5

Typical speed of sound in air

Answer 5

330 m/s

Question 6

Newton’s first law

Answer 6

If resultant force on object is zero:

1) It’s stationary
2) It is moving at the same velocity

Question 7

Inertia

Answer 7

Tendency for an object to continue state of rest or moving at the same speed (uniform motion)

Question 8

Newton’s second law

Answer 8

Acceleration of object proportional to force acting on object and inversely proportional to mass of object

Question 9

Newton’s third law

Answer 9

When two objects interact, forces they exert on eachother are equal and opposite

Question 10

Typical range of human reaction time

Answer 10

0.2 s to 0.9s

Question 11

Example contact forces

Answer 11

Friction, air resistance, tension, normal contact force

Question 12

Non contact examples

Answer 12

Gravitational force
Electrostatic
Magnetic

Question 13

Force vector or scaler

Answer 13

Vector

Question 14

Centre of mass definition

Answer 14

The point where you assume all the mass is concentrated

Question 15

Force definition

Answer 15

A push or pull on object caused by interaction

Question 16

How weight is measured

Answer 16

Calibrated spring balance like Newton metre

Question 17

Forces and doing work

Answer 17

Forces do work to move an object which transfers energy through stores. So force does work when force causes a displacement
Eg pushing something across carpet does work against frictional forces and energy is transferred usefully and dissipated

Question 18

Joules and newton metres

Answer 18

1 J is equal to 1 Nm

Question 19

Spring constant

Answer 19

Dependent on material: stiffer is greater constant

Question 20

Why you need more than one force to change shape of object

Answer 20

Otherwise the object would just move in the direction of the applied force

Question 21

Work done and elastic potential

Answer 21

If the spring isn’t inelastically deformed, the work done on spring is equal to the elastic potential energy stored

Question 22

What creates atmospheric pressure

Answer 22

Air molecules colliding with a surface

Question 23

4 things that affect speed

Answer 23

Fitness
Age
Terrain
Distance travelled

Question 24

What wind speed is affected by

Answer 24

Temperature
Atmospheric pressure
If there are large structures nesrby

Question 25

Uniform acceleration

Answer 25

Constant acceleration: increasing speed at a constant rate

Question 26

When acceleration is uniform

Answer 26

For objects falling: same as gravity (9.8m/s squared) near the earth surface

Question 27

Drag

Answer 27

Resistance in a fluid like air resistance

Question 28

Terminal velocity

Answer 28

When the force of gravity on a falling object equals the drag force and it falls at a steady speed (no resultant force) Friction builds up and reduces acceleration until the resultant force is 0

Question 29

Intertial mass

Answer 29

Measure of how difficult it is for change of velocity in an object Defined as the ratio of force over acceleration

Question 30

What driver reaction times affected by

Answer 30

Tiredness Drugs Alcohol Distraction

Question 31

Momentum symbol

Answer 31

kg m/s

Question 32

How to work out change in momentum

Answer 32

F=ma and a=v-u/t F= m X change in velocity/ change in time MX change in velocity is the rate of change of momentum

Question 33

Typical speed of car

Answer 33

25 m/s

Question 34

Typical speed of train

Answer 34

55 m/s

Question 35

Typical speed of plane

Answer 35

250 m/s

Question 36

Braking distance at 30mph

Answer 36

14m

Question 37

Braking distance at 60mph

Answer 37

55m

Question 38

Braking distance at 70mph

Answer 38

75m

Question 39

Momentum and forces

Answer 39

A greater force means a greater rate of change of momentum

Question 40

Weight

Answer 40

Force acting on an object due to gravity

Question 41

Upthrust is equal to

Answer 41

Weight of fluid displaced by object

Question 42

If object weight is more than upthrus

Answer 42

Object sinks

Question 43

Atmosphere

Answer 43

Thin layer of air round earth

Question 44

Displacement

Answer 44

Distance and direction in straight line from objects starting and finishing point Vector quantity

Question 45

What to do if your answer is approximate value

Answer 45

~

Question 46

Stopping distance

Answer 46

Thinking distance + Braking distance

Question 47

3 factors that affect braking distance

Answer 47

Adverse road conditions Weather conditions Poor quality of vehicle- brakes or tyres

Question 48

When force applied to brakes

Answer 48

Work done by friction force between brakes and wheel reduces kinetic energy and temperature of brakes increases

Question 49

Equipment for measuring speed of sound wave

Answer 49

Signal generator and oscilloscope

Question 50

Equipment for speed of water ripples

Answer 50

Signal generator | Ripple tank

Question 51

Pressure of fluid forces

Answer 51

Force exerted normal to any surface in contact with fluid

Question 52

Terminal velocity step by step

Answer 52

When object starts falling force of gravity much more than frictional forces Object accelerates As speed increases friction builds up Gradually reduces acceleration until resultant force is 0 Terminal velocity reached

Question 53

Emergency stop

Answer 53

Maximum force applied to brakes

Question 54

Icy roads

Answer 54

Less grip so less friction | Leads to skidding

Question 55

Bad brakes

Answer 55

Can’t apply so much force

Question 56

Why faster vehicles need greater braking force

Answer 56

More energy in kinetic stores More work needs to be done to stop it Greater force needed to stop it within a certain distance

Question 57

Why braking distance increases faster as you speed up

Answer 57

Work done to stop car equal to energy in kinetic stores (0.5mv2) As speed doubles kinetic energy increases four fold ( 2 squared) so work done increases four fold

Question 58

Upthrust and weight

Answer 58

Upthrust has to equal weight for an object to float If an object less dense, it weighs less than the fluid so it can displace a volume of water equal to its weight and float as the Upthrust is equal to weight