P3 - Speed, Distance & Acceleration, Mass, Weight, & Gravity, Forces, Friction Forces, Terminal Speed

Question 1

How do you find the speed of an object?

Answer 1

You need to measure the distance it travels and the time it takes, then the speed is calculated in meters per second.

Question 2

For an object, what does a greater speed mean?

Answer 2

The greater the speed of an object, the further the distance it can travel in a certain time, or the shorter the time it takes to go a certain distance.

Question 3

What does the gradient on a distance time graph tell you?

Answer 3

The gradient tells you the speed.

Question 4

What does a flat section on a distance-time graph represent?

Answer 4

The flat section on a distance-time graph represents where the object.

Question 5

What does a steeper gradient represent?

Distance - Time Graphs

Answer 5

The steeper the gradient the greater the speed.

Question 6

What do curved sections on a distance-time graph represent?

Answer 6

They represent acceleration or deceleration.

Question 7

What does a steepening curve represent?(Distance Time Graph )

Answer 7

A steepening curve means it is speeding up ( accelerating )

Question 8

What does a levelling off curve represent?(Distance Time Graph )

Answer 8

A levelling off curve means it is slowing down.

Question 9

What is acceleration?

Answer 9

Acceleration is how quickly speed is changing.

Question 10

What is deceleration?

Answer 10

( A negative Acceleration )

A decrease in speed.

Question 11

On a speed-time graph what does gradient represent?

Answer 11

The gradient represents acceleration.

Question 12

On a speed-time graph what do the flat sections represent?

Answer 12

The flat sections represent steady speed.

Question 13

What does a steeper gradient mean for the acceleration on a speed-time graph?

Answer 13

The steeper the gradient, the greater the acceleration or deceleration.

Question 14

What does a curve mean for an speed-time graph?

Answer 14

A curve means a non uniform ( changing ) acceleration or deceleration.

Question 15

How can you find the distance travelled on a speed time graph?

Answer 15

The distance travelled in any time interval is equal to the area under the graph.

Question 16

What is the speed of an object?

Answer 16

The speed of an object is just how fast it is going, there are no directions involved.

Question 17

What is velocity?

Answer 17

Velocity is a vector, it describes both the speed and direction of an object.

Question 18

What does Gravity do at the surface of a planet?

Answer 18

On the surface of a planet, gravity makes all things accelerate towards the ground, all with the same acceleration, g.

Question 19

what is “g” ( gravitational field strength)?

Answer 19

G is the acceleration due to gravity and is also known as the gravitational field strength.

Question 20

What is the value of “g” on Earth?

Answer 20

The value of “g” on earth is 10 m/s(squared) or 10 N/Kg).
It is different on other planets, and can vary in different places on Earth.
g will be slightly different down a mineshaft compared to the top of a mountain.
It is not affected by changes in the atmosphere.

Question 21

Gravity gives an object its…

Answer 21

Gravity gives an object its weight.

Question 22

What is weight caused by?

Answer 22

Weight is caused by the pull of gravity.

Question 23

What is mass?

Answer 23

Mass is the amount of matter ( or “stuff” ) an object contains. For any given object this will have the same value anywhere in the universe.

Question 24

What is weight measured in?

Answer 24

Weight is a force measured in newtons

Question 25

What is mass measured in?

Answer 25

Mass is not a force, it is measured in kilograms.

Question 26

Why do objects have different weights on the moon and the Earth?

Answer 26

The gravitational pull of the Moon is weaker than the gravitational pull of the Earth.

Question 27

What is a force?

Answer 27

A force is a simply a push or a pull, there are six different types of force.

Question 28

What are the six different types of force?

Answer 28

• Gravity or Weight, always acting straight downwards
• Reaction force from a surface, usually acting straight upwards
• Thrust or push or pull due to an engine or rocket, speeding something up
• Drag or Air resistance or Friction, which is slowing something down
• Lift due to an aeroplane wing
• Tension in a rope or cable.

Question 29

How must the forces be balanced for an object to be stationary?

Answer 29

• The force of gravity ( or weight ) is acting downwards.
• This causes a reaction force from the surface pushing up the object
• This is the only way it can be in balance, the force arrows the same size

Question 30

In a stationary object, why does it need a reaction force?

Answer 30

Without a reaction force it would accelerate downwards due to the pull of gravity.

Question 31

In a stationary object, why must the horizontal forces be equal?

Answer 31

They must equal and opposite, because otherwise the object would accelerate sideways.

Question 32

What is the size of forces in an object travelling at steady horizontal/vertical speed?

Answer 32

All of the forces are balanced.

Question 33

In an object travelling at steady speed, why must all of the forces be equal?

Answer 33

The forces must stay in balance because otherwise you would get acceleration/deceleration, not steady speed.

Question 34

In an object with horizontal/vertical acceleration, why must the force be unbalanced?

Answer 34

• You only get acceleration with an overall resultant ( unbalanced ) force.
• The bigger the unbalanced force, the greater the acceleration
• On a force diagram the arrows will be unequal.

Question 35

What direction does friction act?

Answer 35

When an object is moving ( or trying to move ) friction acts in the direction that opposes movement.

Question 36

What does the force of friction try to do?

Answer 36

The force of friction will match the size of the force trying to move it, up to a point, after this the friction will be less than the other force and the object will move.

Question 37

What is the purpose of friction?

Answer 37

Friction will act to make the moving object slow down and stop.

Question 38

Why do objects need a driving force?

Answer 38

To travel at steady speed, objects always need a driving force to overcome the friction.

Question 39

What are the three main ways in which friction occurs?

Answer 39

• Friction between solid surfaces which are gripping.
• Friction between solid surfaces which are sliding past each other
• Resistance or “drag” from fluids ( liquids or gases, e.g. air).

Question 40

What can increase drag?

Answer 40

The larger the area of the object, the greater the drag.

Question 41

How can objects be changed to reduce drag?

Answer 41

To reduce drag, the area and shape are streamlined and reduced, like wedge shaped sports cars.

Question 42

What design features of cars increase drag?

Answer 42

• Roof boxes on cars spoil the streamlined shape, and they slow down the car.
  Windows can also increase drag, if they are open.

Question 43

How are parachutes designed to slow you down?

Answer 43

Parachutes often have large area to give a high drag to slow you down, for a given thrust the higher the drag, the lower the top speed.

Question 44

In a fluid, how does drag work?

Answer 44

In a fluid, friction (drag) always increases as the speed increases.

Question 45

How do objects reach terminal speed?

Answer 45

• When objects first set off, they have much more force accelerating them than resistance slowing them down.
• As the speed increases the resistance increases as well.
• This gradually reduces the acceleration until the resistance force ( friction or drag ) is equal to the accelerating force ( weight or thrust ) so it can’t accelerate any more. the forces are balanced.
• It will have reached its maximum speed or terminal speed.

Question 46

What does the terminal speed of any moving object depend on?

Answer 46

The terminal speed of any moving object depends on its drag compared to its driving force, ( weight for a falling object, thrust for, e.g. a car ).

Question 47

What effect does drag have on terminal speed?

Answer 47

The greater the drag, the lower the terminal speed of the object.

Question 48

What does drag depend on?

Answer 48

Drag depends on the shape and area.