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science > Unit 9: Application of Forces and Transfer of Energy > Flashcards

Unit 9: Application of Forces and Transfer of Energy Flashcards

1
Q

What is a force (2pts)

A

What is a Force?
* A force is a push or a pull.
* The SI unit for force is newton (N).

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2
Q

Types of Forces
Contact Forces
definition + how many contact forces?

A

Contact Forces
* When an object is touched, contact forces act on it (there is physical contact between 2 surfaces).
- e.g. Friction, Elastic Force, Normal Force, Tension Force

There are 5 contact forces:
Friction
Elastic Force
Normal Force
Resultant Force
Applied Force

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3
Q

Types of Forces
Non-Contact Forces
definition + how many non-contact forces?

A

Non-Contact Forces
* A non-contact force is a force which acts on an object without coming physically in contact with it.
- e.g. Gravitational Force, Magnetic Force

There are 2 non-contact forces:
Gravitational Force
Magnetic Force

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4
Q

Contact Forces
Friction
(3pt)

A

Friction
* force that opposes motion between 2 surfaces in contact
* The mass of object and roughness of the surfaces in contact affects friction!
- When the object is heavier/lighter and when surface is smoother/rougher, the amount of friction produced increases/decreases.

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5
Q

Contact Forces
Applied Force (2pt)

A

Applied Force
* Force which is applied to an object by another object (literally).
* acts in the opposite direction of elastic and tension force.
- e.g. a man pushing a barrel; there is an applied force pushing the barrel

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6
Q

Contact Forces
Elastic Force (2pt)

A

Elastic Force
* force acting on a stretched or compressed elastic object to return to its original shape (e.g. springs)
* acts in the opposite direction of applied force

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7
Q

Contact Forces
Tension Force (2pt)

A

Tension Force
* Tension force is a contact force that occurs when an object is stretched.
* acts in the opposite direction of applied force

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8
Q

Contact Forces
Normal Force (2pt)

A

Normal Force
* Normal Force is defined as the force that a surface exerts on an object.
* The surfaces of the objects must be in contact with each other (perpendicular) and they balance gravitational force/other forces.

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9
Q

Non-contact Forces
Gravitational Force (1-2 impt pt)

A

Gravitational Force
* Force that attracts two objects towards each other.
* Gravity pulls things down.
* Gravity pulls things radically inwards.
* Note: Gravity is not the same as gravitational force!
- Gravitational Force is the acting force between two objects. On the other hand, gravity is the force occurring between an object and the very big object (Earth).

  • Always use Gravitational Force (or weight) to answer qns!
  • e.g. When Earth exerts a gravitational force on an object and pulls it towards its centre, the object has weight. (refer to weight vs mass section)
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10
Q

Non-contact Forces
Magnetic Force (1 impt pt, 4pts)

A

Magnetic Force
* Magnetic force is the push or pull between magnets only or magnets on magnetic materials.
* like poles of magnets facing each other = attraction
* unlike poles of magnets facing each other = repulsion
* magnetic materials (Cobalt, Iron, Nickel and Steel) can attract magnets (but not repel them).

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11
Q

How to measure force? (optional, 1pt)

A

How to Measure Force?
* Forces are measured with force-meters (e.g. spring balances).
* The SI unit of force is the newton (N).
* Equipment (spring balances) than can measure force (= N, weight)
* There are two types of spring balances:
- Compression spring balance (spring is compressed when a force acts on it.)
- Extension spring balance (spring stretches when a pulling force acts on it)

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12
Q

Formula for weight?

A

Weight = mass x acceleration due to gravity
W = mg
* Note: g is a constant known as the acceleration due to gravity & is taken to be ≈ 10 m/s²

  • The weight of an object is the gravitational force acting on that object.
  • Since weight is a force, it is related to the equation
  • typically, 10N = 1kg = 1000g
  • only need to know how to calculate weight!
  • Weight is always linked to normal force (size of arrow drawn for diagrams must be same size in y3-y4)
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13
Q

Effects of a Force on Size and/or Shape of an object (3-4 impt pt)

A
  • The transfer of energy between objects may cause changes in the size and/or shape of an object.
  • e.g. moulding plasticine
  • A force applied on an object can cause a turning effect about a fixed point called a pivot.
  • As the Force increases, the turning effect increases.
  • As the (perpendicular) Distance of the Force from the pivot increases, the turning effect increases.
  • Examples of turning effect of forces include using a fishing rod, opening a door etc.
  • (optional) *Formula for Turning Effect = Force x (perpendicular) distance from the pivot
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14
Q

Effort vs Pivot template answer (reason):

A
  • The distance between the pivot and the force (state source of force) is greater/lesser, hence lesser/greater force is needed to create the turning effect to (purpose).
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15
Q

Load vs Pivot (force) template answer (reason):

A
  • The distance between the pivot (source of force) and the weight of (item) is greater/lesser, hence there is greater/lesser turning effect to (purpose).
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16
Q

What is pressure? (3 pt)

A

Pressure
* Pressure is the force acting perpendicularly per unit area.
* The SI unit for pressure: Pascal (Pa)
* 1 Pa = 1 N/m²

  • Pressure = Force / Area

Factors affecting Pressure
* Force
* Area

  • When force increases/decreases, pressure increases/decreases.
  • When area increases/decreases, pressure increases/decreases.
17
Q

What are the factors affecting pressure?

A

Factors affecting Pressure
* Force
* Area

  • When force increases/decreases, pressure increases/decreases.
  • When area increases/decreases, pressure increases/decreases.
18
Q

What is mass? (1-2pt)

A
  • Mass = Amount of matter in an object (SI Unit = kg, remains constant regardless of location)
19
Q

What is weight? (2-3pt)

A
  • Weight = Gravitational Force exerted on an object (SI Unit = N, changes depending on location)
  • Weight (N) = mass (m) x gravity (g, usually 10 m/s²)
  • Weight (N) can sometimes equal to Force (N) (e.g. when a book is falling)
20
Q

What is work done? (4pt, 5 subpt)

A
  • Work Done (J) = Force (N) x distance (d)
  • Work Done = the force multiplied by the distance moved in the direction of the force.
  • Conditions that must be present for work to be done:
  • There is a force acting on the object.
  • The object moves through a distance.
  • The movement of the object is in the direction of the force.
  • No work is done when:
  • Object does not move.
  • Direction of force is not in the same direction of the movement.
21
Q

Formula for work done?

A
  • Work Done (J) = Force (N) x distance (d)
22
Q

What are the conditions that must be present for work to be done?

A
  • Conditions that must be present for work to be done:
  • There is a force acting on the object.
  • The object moves through a distance.
  • The movement of the object is in the direction of the force.
23
Q

No work is done when:

A
  • No work is done when:
  • Object does not move.
  • Direction of force is not in the same direction of the movement.
24
Q

What is Energy? (4pt, 3subpt)

A

Energy
* Energy is the ability to do work.
* Energy is transferred when work is done.
* Energy is measured in Joules (J).
* the amount of work done on an object is related to :
1. The energy transferred to the object
2. The force applied on the object
3. The distance travelled by the object

25
Q

SI Unit of Energy?

A

Joules (J)

26
Q

SI Unit of Force?

A

Newton (N)

27
Q

SI Unit of mass?

A

kilogram (kg)

28
Q

SI Unit of weight?

A

Newton (N)

29
Q

SI Unit of pressure?

A

Pascal (Pa)

29
Q

Types/Sources of Energy? (15)

A
  • Light Energy
  • Heat Energy
  • Sound Energy
  • Electrical Energy
  • Kinetic Energy
  • Potential Energy
  • Gravitational Potential Energy (GPE)
  • Chemical Potential Energy (CPE)
  • Elastic Potential Energy (EPE)
  • Nuclear Energy (Non-Renewable)
  • Geothermal Energy (heat escaping through volcanoes, geysers and hot springs)
  • Hydroelectric Energy (comes from rain and stored in reservoirs behind dams; water drives the turbines which turn the generators to produce electrical energy)
  • Solar Energy
  • Wind Energy
  • Tidal Energy (difference in the height of water at high tide and low tide is used to generate electricity)
  • Fossil Fuels (Non-renewable)
30
Q

What is the meaning of non-renewable sources of energy?

A
  • Non-renewable sources of energy
  • Sources are limited and will run out one day
31
Q

What is the meaning of renewable sources of energy?

A
  • Renewable sources of energy
  • Sources can be sustained or renewed indefinitely due to unlimited supplies or new growth of organisms.
32
Q

SI Unit for work done?

A

Joules (J)

33
Q

How are energy and work done related? (4-5pt)

A

How are Energy and Work related?
* When work is done, energy is transferred from one thing to another.
* As energy is the ability to do work, therefore:
Work done = Energy transferred
* The unit of work (force), joules (J), is also the unit for energy.
- When one joule of work is done, one joule of energy is transferred.
* When work is done on an object, energy is converted from one form to another (BUT CANNOT BE
DESTROYED!)

34
Q

How to calculate GPE?

A

GPE = Weight (N) x perpendicular distance from ground (m)

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