Physics- Forces and motion

Question 0

Weight

Answer 0

W = mg

Question 1

Acceleration

Answer 1

a = v - u/t

Question 2

Force (acc)

Answer 2

F = Ma

Question 3

[P2] Momentum

Answer 3

p = mv

Question 4

[P2] Force (momentum)

Answer 4

F = mv - mu / T

Question 5

Moment

Answer 5

Moment (Nm) = f x perpendicular d from pivot

Question 6

Orbital speed

Answer 6

v = 2 PI r / T

Question 7

Distance time graphs

Gradient = ?
Flat = ?
Curves = ?
Downhill means ?

Answer 7

Gradient = speed/steady speed
Flat = stopped moving
Curves = acceleration/deceleration
Downhill means going back towards starting point.

Question 8

Velocity time graphs

Gradient = ?
Flat = ?
Uphill means?
Downhill means?
Area under graph?
Curve?

Answer 8

Gradient = acceleration
Flat = steady speed
Uphill means acceleration 
Downhill means deceleration 
Area under graph is distance 
Curve means changing acceleration

Question 9

Experiment to show average speed

Mass affects speed?
Friction affects speed?
Acceleration?

Answer 9

Toy car on a ramp:

1. Mark a line on ramp so car starts at same point each time
2. Measure distance between each light gate (3)
3. Let go of car just before light gate
4. Light gates connected to a pc- when car passes it breaks beam of light, time recorded by data loggers
5. Repeat and get average time -> more reliable
6. Find average speed

Load weights onto car
Lay different materials flat
Starting car at different places on ramp

Question 10

Experiment on free fall

Answer 10

Sycamore seeds- small weight, large s.a.

1. Collect a bunch, weigh them and measure wing length
2. Use seeds with similar mass but diff wing lengths
3. Drop seeds from same height
4. Use stopwatch - how long to fall to ground
5. Repeat - find average time
6. Plot graph

Question 11

First law of motion

Answer 11

Balanced forces mean no change in velocity

ZERO RESULTANT FORCE

Question 12

Second law of motion

Answer 12

A resultant force means Acceleration

Unbalanced force = object accelerate in that direction

Question 13

The bigger the force, acceleration?

Th bigger the mass, acceleration?

Answer 13

Bigger the force, greater the acceleration

Bigger the mass. Smaller the acceleration

Question 14

[P2] Third law of motion

Answer 14

If object A exerts a force on object B, object B exerts the EXACT OPPOSITE force on object A

Question 15

[P2] Vector quantities?

Scalar quantities ?

Examples of each

Answer 15

Vector - size and direction
Force, velocity, acceleration, momentum

Scalar - size
Mass, temperature, time, length

Question 16

Stopping distance is

Answer 16

Thinking distance + braking distance

Question 17

Thinking distance is…

Answer 17

Distance car travels in time between driver noticing hazards and applying brakes

Question 18

Braking distance is…

Answer 18

Distance car travels during its deceleration whilst brakes are being applied

Question 19

Thinking distance affected by…

Answer 19

How fast you’re going

How DOPEY you are - tiredness, drugs, alcohol, old age

Question 20

Braking distance affected by…

Answer 20

How fast you’re going

Mass of vehicle - larger mass, longer takes to stop

Conditions of brakes

Grip - road surface, weather conditions, tyres

Question 21

[P2] larger the force, ? Change of Momentum so a ? Acceleration

Answer 21

Larger the force, faster change of momentum, greater acceleration

Question 22

[P2] how are cars designed to lessen injuries in a car crash? How?

Answer 22

CRUMPLE ZONES crumple on impact
Increasing time taken for car to stop

SEAT BELTS stretch slightly
Increasing time taken for wearer to stop- reduces forces acting on chest

AIR BAGS
Slow you down gradually

Longer it takes for change in momentum, smaller the force, less severe injuries

Question 23

Larger force means ? Moment

Longer lever, ? Force, ? Moment. Why?

To get maximum moment… Why?

Answer 23

Larger force means larger moment

Longer lever means same force can exert a larger moment because distance from pivot is greater

To get maximum moment, push at right angles - perpendicular to lever because at any other angle means smaller moment as perpendicular d from pivot is smaller

Question 24

How do you find centre of gravity of any shape?

Answer 24

1. Suspend shape and plumb line for same point, wait until stops moving
2. Draw a line along plumb line
3. Do the same but suspend shape from different pivot point
4. Centre of gravity is where two lines cross

Question 25

What is the principle of moments?

Answer 25

If an object balanced,

Total a.clockwise moments = total clockwise moments

Question 26

What is Hooke’s law

Answer 26

Extension is proportional to force

Question 27

Experiment Hooke’s law

Answer 27

1. Have a weighted stand, clamp, hanging masses, spring
2. Measure length of spring when no mass on it
3. Add one mass, measure length
4. Repeat 6 times
5. Repeat exp, calculate average length for each weight

Question 28

What’s a galaxy

Answer 28

Large collection of stars

Question 29

Geostationary satellites
Orbital period?
Used for?
Why?

Answer 29

Orbital period of One day

Communications
Always over same part of the planet

Question 30

Comets

What are they
Orbits
Speed of orbits

Answer 30

Small lumps of icy rock

Very elliptical orbits around the sun

Travels much faster when near sun because GPE decreases, KE increases