P5 (part 1) Flashcards

1
Q

What is a scalar quantity + example?

A

it is a quantity with a magnitude (size) only

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

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2
Q

What is a vector quantity + example?

A

it is a quantity with a magnitude and an associated direction

example: forces , displacement, acceleration and velocity

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3
Q

How are vectors represented?

A

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

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4
Q

What is a force?

A

is a ‘push’ or ‘pull’

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5
Q

How can forces be categorised?

A

contact or non-contract

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6
Q

What are examples of contact force?

A
  • friction
  • air resistance
  • tension
  • normal contact force (reaction force)
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7
Q

What are examples of non-contact force?

A
  • gravitational force (weight)
  • electrostatic force
  • magnetic force
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8
Q

Why are forces considered to be vectors?

A

they have both a size and direction

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9
Q

What are the summary of common forces?

A

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

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10
Q

What is mass?

A

the amount of matter an object can contain

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11
Q

What is mass measured in?

A

kg

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12
Q

Why is weight a vector?

A

it has a magnitude and a direction

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13
Q

What is weight?

A

is the force acting on an object due to gravity

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14
Q

What causes the force of gravity around the Earth?

A

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

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15
Q

What are the units of weight?

A

newtons (N)

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16
Q

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

A

if the mass of an object doubles so will the weight

the relationship between mass and weight are ∝

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17
Q

Why can weight change?

A

because it depends on the strength of gravity

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18
Q

How can we calculate the weight of an object?

A

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

W= mg

19
Q

How can we measure the weight of an object?

A
  • scale/balance

- or a newton meter

20
Q

What is the centre of mass of an object?

A

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

21
Q

What is meant by the ‘resultant force’?

A

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

22
Q

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

A
  • it can speed up
  • it can slow down
  • it can change direction
23
Q

How about if the forces are balanced?

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

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

24
Q

What is work done?

A

when a force makes an object move a certain distance

25
What is another way of saying work done?
energy transferred
26
What is the unit of work done?
joules (J)
27
During a race, a car brakes can glow red hot. Explain why, using ideas about work
- 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
28
What is the equation for work done?
work = force x distance moved W = fs
29
What is the alternative unit for work done?
newtons meters (Nm) | 1Nm = 1J
30
What are the 4 energy equation?
``` Ep = mgh Ek = 1/2mv2 E = Pt E = QV ```
31
When a force is applied to an object, what 3 thing can happen?
the object can: - bend - stretch - compress
32
More than one force needs to be acting. Why?
more than one force needs to be acting, otherwise the object would simply move in the direction of the force applied
33
What are the 2 types of deformation?
- elastic | - inelastic
34
What happens in elastic deformation?
an object that goes back to its original shape after a force has been removed has been elastically deformed
35
What happens in inelastic deformation?
an object that does not go back to its original shape after a force has been removed has been inelastically deformed
36
What is meant by the 'elastic limit'?
if a spring is stretched until it permanently deforms, we say it has reached its elastic limit
37
What is the equation for Hooke's Law?
force (N) = spring constant (N/m) x extension (m) F = Ke
38
What is the limit of proportionality?
the point at which the spring will no longer return to its original length
39
What happens to a spring once it is stretched beyond this point(its elastic limit)?
it is permanently deformed
40
How can you see where the limit of proportionality is from a graph of force against extension?
when the line starts to curve
41
What happens to the the energy to an object when work is done?
energy will be transferred to the elastic potential energy store of the object
42
What happens to the the energy to an object when it is elastically deformed?
then all of this energy is transferred to the object elastic potential energy store
43
What is the definition for elastic potential energy?
the amount of energy stored in a spring
44
What is the formula for elastic potential energy?
elastic potential energy (J) = 0.5 x spring constant (N/m) x extension2 (m) Ee = 0.5ke2