Forces And Motion

Question 1

How can you measure force?

Answer 1

Using a Newton balance or a spring balance

Question 2

What force always opposes motion?

Answer 2

Friction

Question 3

How can friction be reduced?

give some examples too

Answer 3

By keeping he moving surfaces apart?

Example: lubrication (e.g. Oil), cushion or air (e.g. Hovercraft)

Question 4

A force is something that can:

Answer 4

1. Start or stop an object moving
2. Speed up or slow down a moving object
3. Change the direction in which an object is moving
4. Make an object rotate
5. Change the shape of an object

Question 5

What unit is force measured in?

Is force weight/mass?

Answer 5

Newtons (N)

Force is weight NOT MASS

Question 6

How can you find the weight of an object if you know it’s mass?

Answer 6

Multiply it’s mass by 10 (more precisely 9.8)

Question 7

The frictional force between two surfaces is proportional to ???

Answer 7

The force pressing them together

Question 8

What page are you about to go to in the revision booklet to revise elastic limit etc

Answer 8

Page 4 and 5

Question 9

What is the resistive force (approximately) equal to?

Answer 9

The speed squared

Question 10

What is the drag force when the object STARTS to fall?

Answer 10

The drag force is zero

Question 11

When is terminal velocity reached?

Answer 11

When the drag force is equal to the weight

Question 12

What is the stopping distance?

Answer 12

The thinking distance (distance travelled while thinking about braking) + the braking distance (distance travelled one the brakes have been applied)

Question 13

What is thinking distance proportional to?

Answer 13

The speed

Question 14

What does reaction time depend on?

Answer 14

Age, eyesight, tiredness, alcohol, drugs, medication, etc

Question 15

The braking distance will be larger if:

Answer 15

1. The speed is higher
2. The braking force is smaller
3. The mass of the at is larger

Question 16

How does a helical steel spring stretch between A and B?

Answer 16

Uniformly

Question 17

What happens at B for a helical steel spring?

Answer 17

It reaches it’s elastic limit and the extensions become much larger

Question 18

When a helical steel spring has been unloaded after passing its elastic limit what happens to it?

Answer 18

It has a permanent stretch

Question 19

How does a copper wire stretch between A and B?

Answer 19

Uniformly

Elastically

Question 20

What does it mean when something is described as elastic?

Answer 20

When the unloading line matches the loading line

Question 21

What happens between B and C to a copper wire?

Answer 21

The wire yields and exhibits plastic flow

The extension become much larger

Question 22

What is a vector quantity and give 6 examples

Answer 22

A quantity where direction is important, its not just about magnitude.
Displacement, velocity, momentum, acceleration, force, weight

Question 23

Relationship between momentum, mass and velocity

Answer 23

momentum = mass x velocity

Question 24

What is the big rule of momentum and what is it called

Answer 24

Momentum is conserved - the Principle of Conservation of Momentum

Question 25

Relationship between force, change in momentum and times

Answer 25

F = (mv - mu) / t

Question 26

What is the rule when it comes to moments at a pivot?

Answer 26

The sum of the clockwise moments = the sum of the anticlockwise moments

Question 27

Relationship between force, mass and acceleration

Answer 27

Force (N) = mass (kg) x acceleration (m/s/s)