Forces And Motion

Question 1

What is the difference between speed and velocity

Answer 1

Velocity requires a specific direction of travel

Question 2

What is acceleration

Answer 2

A measurement to describe the change in velocity
Can be caused by a change in speed or a change in direction

Question 3

What does the gradient of a distance time graph show

Answer 3

The speed

Question 4

What does a flat section show in a distance time graph

Answer 4

A stationary object

Question 5

What does a curve show in a distance time graph

Answer 5

Acceleration

Question 6

What does the gradient show in a velocity time graph

Answer 6

Acceleration

Question 7

What does a flat section represent in a velocity time graph

Answer 7

A steady speed

Question 8

What does the area under the graph of a velocity time graph show

Answer 8

Distance traveled in that time interval

Question 10

What is gravity and what are its effects

Answer 10

The force of attraction between all masses
It gives everything a weight
Keeps moons, planets and satellites in orbit
Causes objects to accelerate towards the ground

Question 11

What is weight

Answer 11

The force caused by the pull of gravity pulling an object down to Earth

Question 12

What is friction

Answer 12

A force that opposes motion

Question 13

What are the 3 main ways in which friction acts

Answer 13

Between solid surfaces that are gripping

Between objects sliding past each other

Resistance/drag from fluids

Question 14

How can you reduce sliding friction

Answer 14

Adding a lubricant like oil or grease between the surfaces

Question 15

How can you reduce resistance/drag

Answer 15

Ensure the shape of the object streamlined
In a fluid, friction always increases as speed increases

Question 16

How can you investigate the motion of a toy car on a ramp

Answer 16

Mark a line on the ramp to ensure that the start point is always the same
Measure the distance between each light gate
Let go of the car so it rolls down the slope
The light gates should be connected to a computer, when the car rolls past them a beam of light should be broken and a time is recorded by data-logging software
Repeat the experiment and record an average time to reach each light gate
Find the average speed by dividing the distance by the average time

Question 17

How could you investigate acceleration due to gravity with this setup

Answer 17

Placing the car higher up the ramp

Question 18

What is the Newton’s first law of motion

Answer 18

If the forces are balanced then there will be no change in velocity
To keep at a steady speed, there must be no resultant force

Question 19

What is Newton’s second law of motion

Answer 19

If there is an unbalanced force, then the object will accelerate in that direction

Question 20

What affects acceleration

Answer 20

The bigger the force, the greater the acceleration or deceleration
The bigger the mass, the smaller the acceleration

Question 21

What is Newton’s third law of motion

Answer 21

If object A exerts a force on object B, then object B exerts an equal and opposite force on object A

Question 22

What is a vector quantity

Answer 22

One in which has size and direction
E.g. velocity, acceleration, force

Question 23

What is a scalar quantity

Answer 23

One in which only has size
E.g. mass, temperature, time

Question 24

Outline the theory of terminal velocity

Answer 24

When an object starts to fall, it has a greater acceleration than resistance
As its velocity increases, so does its resistance
This resistance builds up and reduces acceleration until eventually the resistance force is equal to the driving force
This means the object can no longer accelerate and has reached its terminal velocity

Question 25

Why does a parachute cause an object to slow down

Answer 25

Increased air resistance as the parachute gathers more air particles, increased resistance reduces the driving force

Question 26

What does Hooke’s law state

Answer 26

That extension is proportional to Force

Question 27

How can you investigate Hooke’s law with a spring

Answer 27

Measure the length of the spring when no load is applied Add one mass at a time and measure the spring at rest, the extension is the change in length from the original length Repeat this process until enough measurements are made Repeat the experiment and calculate a mean average for length of the spring for each applied weight Increased mass = increased extension

Question 28

What causes the prevention of Hooke’s law being obeyed

Answer 28

Elastic limit, if elastic limit is exceeded, then the material will be permanently stretched

Question 29

What is elastic behaviour

Answer 29

The ability for an object to return to its original shape following removal of forces after being stretched

Question 30

What is thinking distance and what affects it

Answer 30

The distance in between the driver noticing the hazard and applying the brakes How fast you are going and the reaction time of the driver (age, alcohol consumption etc.)

Question 31

What is braking distance and what affects it

Answer 31

The distance the car travels during deceleration while the brakes are being applied The mass of the vehicle, the quality of brakes, weather, and road surface

Question 32

What is Stopping Distance

Answer 32

Thinking Distance + Braking Distance

Question 33

What is the conservation of momentum

Answer 33

Momentum is conserved in a closed system with the absence of external forces, total momentum before a collision is equal to total momentum after a collision

Question 34

What safety precautions protect a driver in a car

Answer 34

Seat belts stretch slightly, increasing the time for the wearer to stop, reducing the forces acting on their chest Air bags slow you down more gradually Crumple zones crumple on impact, increasing the time taken for the car to stop

Question 35

What is a moment

Answer 35

The turning effect of a force

Question 36

How can you increase the size of a moment

Answer 36

Applying a larger force Increasing the distance from the pivot Pushing at right angles to the pivot to maximise perpendicular distance

Question 37

What is centre of gravity and how would you find it on any flat shape

Answer 37

The point through which the weight of a body acts Look for lines of symmetry Or suspend the shape and a plumb line from the same point and wait until they stop moving Draw a line along the plumb line, do the same thing again but from a different pivot point The centre of gravity is where the two lines cross

Question 38

What does the principle of moments state

Answer 38

If an object is balanced then the total anticlockwise moments is equal to the total clockwise moments

Question 39

What causes an object to turn

Answer 39

If the moments are not equal, there will be a resultant moment