P5 (part 1)

Question 1

What is a scalar quantity + example?

Answer 1

it is a quantity with a magnitude (size) only

example: mass, speed, volume, energy, time, distance and power

Question 2

What is a vector quantity + example?

Answer 2

it is a quantity with a magnitude and an associated direction

example: forces , displacement, acceleration and velocity

Question 3

How are vectors represented?

Answer 3

by an arrow. The length of the arrow represent the size and the direction of the arrow represents the direction of the vector

Question 4

What is a force?

Answer 4

is a ‘push’ or ‘pull’

Question 5

How can forces be categorised?

Answer 5

contact or non-contract

Question 6

What are examples of contact force?

Answer 6

• friction
• air resistance
• tension
• normal contact force (reaction force)

Question 7

What are examples of non-contact force?

Answer 7

• gravitational force (weight)
• electrostatic force
• magnetic force

Question 8

Why are forces considered to be vectors?

Answer 8

they have both a size and direction

Question 9

What are the summary of common forces?

Answer 9

acting down :
- weight

acting up :
- lift, normal reaction force, upthrust (buoyancy)

acting to cause forward motion:
- thrust

acting to oppose forward motion:
- friction, air/water resistance tension

Question 10

What is mass?

Answer 10

the amount of matter an object can contain

Question 11

What is mass measured in?

Answer 11

kg

Question 12

Why is weight a vector?

Answer 12

it has a magnitude and a direction

Question 13

What is weight?

Answer 13

is the force acting on an object due to gravity

Question 14

What causes the force of gravity around the Earth?

Answer 14

because the Earth is massive( it has alot of mass in physics)

Question 15

What are the units of weight?

Answer 15

newtons (N)

Question 16

What do we mean when we say mass and weight are ‘directly proportional’?

Answer 16

if the mass of an object doubles so will the weight

the relationship between mass and weight are ∝

Question 17

Why can weight change?

Answer 17

because it depends on the strength of gravity

Question 18

How can we calculate the weight of an object?

Answer 18

weight (N) = mass (kg) x gravitational field strength (m/s)

W= mg

Question 19

How can we measure the weight of an object?

Answer 19

• scale/balance

- or a newton meter

Question 20

What is the centre of mass of an object?

Answer 20

is defined as ‘the point at the weight of an object can be considered to act

Question 21

What is meant by the ‘resultant force’?

Answer 21

is a single force that can replace all of the other forces acting on something

Question 22

What can happen to an object if the forces acting on it are unbalanced?

Answer 22

• it can speed up
• it can slow down
• it can change direction

Question 23

How about if the forces are balanced?

Answer 23

• stays at rest (if it’s already not moving)

- move at a constant speed in the same direction (if it’s already moving)

Question 24

What is work done?

Answer 24

when a force makes an object move a certain distance

Question 25

What is another way of saying work done?

Answer 25

energy transferred

Question 26

What is the unit of work done?

Answer 26

joules (J)

Question 27

During a race, a car brakes can glow red hot. Explain why, using ideas about work

Answer 27

• when the driver presses the brake the force of friction acts on the brake disk
• this force doesn’t work on the car, causing it to slow down or stop
• as work is being done, energy is transferred from the kinetic store of the car to the thermal store of the brakes causing them to glow red hot

Question 28

What is the equation for work done?

Answer 28

work = force x distance moved

W = fs

Question 29

What is the alternative unit for work done?

Answer 29

newtons meters (Nm)

1Nm = 1J

Question 30

What are the 4 energy equation?

Answer 30

Ep = mgh
Ek = 1/2mv2
E = Pt
E = QV

Question 31

When a force is applied to an object, what 3 thing can happen?

Answer 31

the object can:

• bend
• stretch
• compress

Question 32

More than one force needs to be acting. Why?

Answer 32

more than one force needs to be acting, otherwise the object would simply move in the direction of the force applied

Question 33

What are the 2 types of deformation?

Answer 33

• elastic

- inelastic

Question 34

What happens in elastic deformation?

Answer 34

an object that goes back to its original shape after a force has been removed has been elastically deformed

Question 35

What happens in inelastic deformation?

Answer 35

an object that does not go back to its original shape after a force has been removed has been inelastically deformed

Question 36

What is meant by the ‘elastic limit’?

Answer 36

if a spring is stretched until it permanently deforms, we say it has reached its elastic limit

Question 37

What is the equation for Hooke’s Law?

Answer 37

force (N) = spring constant (N/m) x extension (m)

F = Ke

Question 38

What is the limit of proportionality?

Answer 38

the point at which the spring will no longer return to its original length

Question 39

What happens to a spring once it is stretched beyond this point(its elastic limit)?

Answer 39

it is permanently deformed

Question 40

How can you see where the limit of proportionality is from a graph of force against extension?

Answer 40

when the line starts to curve

Question 41

What happens to the the energy to an object when work is done?

Answer 41

energy will be transferred to the elastic potential energy store of the object

Question 42

What happens to the the energy to an object when it is elastically deformed?

Answer 42

then all of this energy is transferred to the object elastic potential energy store

Question 43

What is the definition for elastic potential energy?

Answer 43

the amount of energy stored in a spring

Question 44

What is the formula for elastic potential energy?

Answer 44

elastic potential energy (J) = 0.5 x spring constant (N/m) x extension2 (m)

Ee = 0.5ke2