Forces P1

Question 1

Types of forces

Answer 1

• non contact (magnetic force)
• contact (reaction force)
• electrostatic force
• friction
• air resistance
• gravitational force

Question 2

What do opposite charges and like charges do

Answer 2

• opposites attract

- like repel

Question 3

What is Newton’s first law of motion

Answer 3

• if the resultant force acting on a stationary object is zero then the object will remain stationary
• if the resultant forcing acting on a MOVING object is zero, then the object will continue moving in the same direction at the same speed (with the same velocity)

(An object will stay stationary or continue moving at the same speed and direction, unless a resultant force is applied)

Question 4

Work done equation

Answer 4

work done (j) = force (n) x distance (d)

Question 5

What are the types of energy transfer

Answer 5

• mechanical work (a force moving an object through a distance)
• electrical work (charges moving due to a pd)
• heating (due to temp difference caused electrically or by chemical reaction
• radiation (energy transferred as a wave like light (radiation) and infrared (radiation) which are emitted from the sun)

Question 6

What will happen if we take away the forces acting on elastic materials

Answer 6

• they will always return to their original length or shape

Question 7

What is elastic deformation

Answer 7

When the elastic changes shape

Question 8

What is the difference between elastic and in elastic deformation

Answer 8

• elastic deformation is reversed when the force is removed

- inelastic deformation is not fully reversed when the force is removed (there is a permanent change in shape)

Question 9

What do you have to do in order to change an objects shape or length

Answer 9

Apply more than one force

Question 10

What would happen if you only applied one force to a stationary object

Answer 10

The forces are no longer balanced, so the object would simply move rather than change shape or length

Question 11

Example of inelastic materials

Answer 11

• certain polymers

Question 12

What is the calculation for the force needed to stretch an elastic object OR compression when an elastic object is squeezed

Answer 12

Force (n) = spring constant (n/m) x extension (m) OR compression (m)

F = k x e

Question 13

What is only true if an object is not inelastically deformed

Answer 13

• when stretching or compressing an elastic object, we’re using a force to do work (elastic potential energy is stored in object)
• work done is equal to the elastic potential energy

Question 14

What are contact forces and non contact forces

Answer 14

• contact (physically touching)

- non contact (physically separated)

Question 15

What are examples of a contact force

Answer 15

• Tension in a rope
• friction
• air resistance
• normal contact force (can only happen if the two objects are in direct contact)

Question 16

Examples of non contact force

Answer 16

• gravitational force
• electrostatic force (the force between two charged objects)
• magnetic force

Question 17

What do objects with opposite charges experience

Answer 17

An electrostatic force of attraction

Question 18

What’s the difference between velocity and speed

Answer 18

• velocity has a direction and so is a vector quantity

Question 19

What is a scalar quantity

Answer 19

When something has magnitude but no direction

Question 20

What is the speed calculation

Answer 20

speed (m/s) = distance (m) divided by time (s)

In triangle distance is at the top

Question 21

What does displacement tell us

Answer 21

• The distance that an object moves in a straight line from the start point to the finish point
• it is a vector quantity as it includes the direction and magnitude

Question 22

What must displacement include

Answer 22

The direction of that straight line

Question 23

What is speed

Answer 23

A scalar quantity as it does not involve direction

Question 24

What are the typical speeds

Answer 24

• normal walking speed = 1.5m/s
• running speed= 3m/s
• cycling speed= 6m/s
• car on a main road= 13m/s
• fast train in the uk= 50m/s
• cruising aeroplane= 250m/s

Question 25

What does speed depend on

Answer 25

- age - fitness (whether they were fitter or unfit) - the terrain (uphill would be slower and flatter would be faster) - distance travelled

Question 26

What is the typical value of speed of sound in air

Answer 26

- 330m/s but the speed in air can vary depending on the weather (speed travels faster on warmer days rather than colder days)

Question 27

Speed of a moving object…

Answer 27

The speed of a moving object is rarely constant

Question 28

Distance travelled by an object moving at a constant speed (average speed) calculation

Answer 28

Distance (m) = speed (m/s) x time (s)

Question 29

What is velocity

Answer 29

- A vector quantity - it includes both magnitude and direction - it’s an objects speed in any direction

Question 30

How is velocity calculated

Answer 30

The same way as speed, just state the direction they are going in

Question 31

What happens to the velocity of an object if it’s moving at a constant speed in a circle

Answer 31

The velocity is constantly changing even though it’s speed stays constant

Question 32

How can an object moving along a straight line be presented in terms of distance

Answer 32

A distance time graph

Question 33

How do you work out the speed on a distance time graph

Answer 33

Using the gradient which is, distance travelled divided by time taken

Question 34

What does an upwards curve on a distance time graph mean

Answer 34

The object is constantly increasing in speed (accelerating)

Question 35

What does the acceleration tell us

Answer 35

The change in it’s velocity over a given time

Question 36

Calculation for acceleration

Answer 36

Change in velocity (m/s) ————————————- = acceleration (m/s2) Time (s) Change in velocity is at the top of triangle

Question 37

What do you do if the velocity in a question reduces (acceleration)

Answer 37

Take it away, if it was reduces to zero from 6 you would do 0-6=-6

Question 38

What do you have if you end up with a negative number in a question (acceleration)

Answer 38

- the object is slowing down and decelerating | - deceleration

Question 39

What does the gradient of a velocity time graph tell us

Answer 39

The acceleration of the object

Question 40

What does it mean if the line is horizontal on a velocity time graph

Answer 40

The object is travelling at a constant speed

Question 41

What is the calculation for acceleration on a velocity time graph

Answer 41

``` Final velocity (m/s) - initial velocity (m/s) ——————————————————- Time (s) = Acceleration (m/s squared) ```

Question 42

What does the total area under the graph tell us and how do we find it (velocity time graph)

Answer 42

- The displacement (the distance travelled in a specific direction) - when we see constant acceleration or deceleration, we divide the graph into shapes and calculate their total area then add them together

Question 43

How to calculate the total area of a velocity time graph when the deceleration and acceleration are not constant

Answer 43

- Count the number of squares complete or almost complete - estimate the number of squares remaining - add the numbers together - mulitiply the number of squares by the total area of one square

Question 44

What is air resistance

Answer 44

An upward force of friction

Question 45

What is it called when an object stops accelerating and moves at a constant velocity

Answer 45

Terminal velocity

Question 46

What will a greater force of friction result in (in terms of acceleration)

Answer 46

A lower terminal velocity

Question 47

What is it called when something is moving at a constant speed and there must be an equal force acting to the right

Answer 47

- The resistive forces | - they include friction with the air and friction with the road (in terms of car)

Question 48

What does a resultant force cause

Answer 48

An objects speed to change or an objects direction