P5 (2)

Question 1

Describe the investigation between force and extension on a spring

Answer 1

Measure natural length of the spring with a millimetre ruler clamped to the stand
Take a reading at eye level and add a marker ( thin strip of tape) to the bottom of the spring
Add a mass to the spring and allow it to come to rest
Record the mass and measure the new length
The extension is the change in length
Repeat this process at least 6 times
Plot a force extension graph of your results

Question 1

How can you tell if the relationship is linear or non-linear with the line of best fit

Answer 1

If the line of best fit is a straight line - linear
If the line of best fit begins to bend - non-linear

Question 2

What is the difference between distance and displacement

Answer 2

Distance - scalar - how far an object moves - no direction
Displacement - vector - how far an object has move from their original point - has a direction

Question 3

Describe the factors that can affect the speed in which a person can walk, run or cycle

Answer 3

Age, terrain, fitness and distance travelled

Question 4

Other than moving objects what also can vary in its speed

Answer 4

The speed of sound and the speed of the wind also vary.

Question 5

Describe the typical every day speeds for a person : walking, running, cycling. A car, train, plane and sound (in air)

Answer 5

Walking - 1.5 m/s
Running - 3 m/s
Cycling - 6 m/s
Car - 25 m/s
Train - 30 m/s
Plane - 250 m/s
Sound - 330 m/s

Question 6

What does the speed of sound and wind depend on

Answer 6

Depends on what the sound waves are travelling through
Temperature, atmospheric pressure and if there are any large buildings nearby

Question 7

Explain how a motion in a circle involves constant speed but changing velocity

Answer 7

As direction is always changing, velocity is changing but speed is not changing

Question 8

From a distance-time graph, how can the speed of a object be calculated

Answer 8

The speed of an object can be calculated from the gradient of its distance–time graph.

Question 9

If an object is accelerating, how can speed be determined

Answer 9

If an object is accelerating, its speed at any particular time
can be determined by drawing a tangent and measuring the
gradient of the distance–time graph at that time

Question 10

On a distance-time graph, how do you find the velocity on a curve

Answer 10

Draw a tangent then work out gradient

Question 11

What does a flat line on a velocity time graph tell us

Answer 11

Object is moving at constant velocity

Question 12

What does the gradient of a velocity time graph tell us

Answer 12

Acceleration/Deceleration of an object

Question 13

How do you work out the distance in a velocity time graph

Answer 13

Straight line : area of strips
Curve: number of squares

Question 14

When is terminal velocity reached

Answer 14

When resultant force is 0
Weight has the same magnitude as air resistance

Question 15

What does the size of air resistance depend on

Answer 15

Surface area and velocity

Question 16

What is newtons first law of motion

Answer 16

A resultant force is required to change the motion of an object

Question 17

What is newtons second law of motion

Answer 17

When a non-zero resultant force acts on an object, it will accelerate
Size of the resultant force is directly proportional to the acceleration it causes

Question 18

Describe how the moon is always accelerating although it moves at constant speed

Answer 18

Moves in a circular motion
Direction is always changing
Velocity is changing
Acceleration is changing

Question 19

Define the term ‘inertia’ and ‘inertial mass’

Answer 19

Tendency for the motion of an object to remain unchanged
How difficult it is to change an objects velocity (mass/acceleration)

Question 20

What is newtons third law

Answer 20

Whenever two objects interact, the forces they exert on each other are equal and opposite.

Question 21

What is stopping distance

Answer 21

total distance a car travels from the moment the driver first notices an obstruction
(thinking distance + braking distance)

Question 22

What is the range for typical reaction time
Describe factors that may increase thinking distance

Answer 22

2-9ms
Drugs
Alcohol
Tiredness

Question 23

Describe the factors that may increase braking distance

Answer 23

Ice on the road
Worn out brakes
Worn out tyres

Question 24

If a vehicle drives three times as fast, what happens to breaking distance

Answer 24

Breaking distance increases by 9 times

Question 25

Which factor increases both thinking and breaking distance

Answer 25

Speed of a vehicle

Question 26

When does newtons third law not apply

Answer 26

When the two interacting forces are different

Question 27

Describe the events of someone skydiving

Answer 27

Initially, weight downwards much larger than air resistance upwards (resultant force in a downwards direction) - accelerates towards the ground
As object accelerates and velocity increases, air resistance increases (collides with more air particles)
Until air resistance = weight - no resultant force - terminal velocity reached

Question 28

Describe the events of someone opening their parachute

Answer 28

Surface area increases massively, collides with more air particles, air resistance increases, resultant force is upwards, decelerate downwards
More they slow down, the lower the air resistance till it equals weight again - no resultant force - new terminal velocity (lower than initial terminal velocity)

Question 29

What happens when a force is applied to the brakes of a vehicle

Answer 29

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

Question 30

As braking force increases what happens and also describe the dangers of large decelerations

Answer 30

The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control

Question 31

Describe the conservation of momentum

Answer 31

In a closed system, total momentum before the collision = total momentum after the collision