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KA S3 Physics > 3. Forces > Flashcards

3. Forces Flashcards

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1
Q

State the 3 effects a force can have on an object.

A

A force can change an objects:
* Speed
* Shape
* Direction

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2
Q

What is the definition of mass?

A

Mass is a measure of how much matter is contained in an object.

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3
Q

What are the units of mass?

A

Kilograms (kg)

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4
Q

What is the definition of weight?

A

Weight is a force exerted on an object’s mass due to gravity.

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5
Q

What are the units of weight?

A

Newtons (N)

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6
Q

What is meant by the term ‘gravitational field strength’?

A

Gravitational field strength is the force experienced per unit mass by an object in a gravitational field.

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7
Q

What are the units of gravitational field strength?

A

Newtons per kilogram (N/kg)

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8
Q

What is the gravitational field strength on Earth?

A

On Earth, g = 9.8 N/kg

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9
Q

How do you rearrange W = mg to calculate mass?

A

m = W/g

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10
Q

What is friction?

A

Friction is a force that opposes the motion of an object.

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11
Q

Which direction does friction act in

A

Friction ALWAYS acts in the opposite direction to the motion of the object.

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12
Q

What type of energy is produced when friction acts on an object?

A

Heat energy

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13
Q

State an example of where friction might be useful and how it could be increased.

A
  • Bring a car to a stop - use a deeper tyre tread.
  • Starting a fire with a stick - push down on the stick more to push the surfaces closer together.
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14
Q

State an example of where friction is not useful and how we can decrease it.

A
  • Hinges of doors - we can lubricate the hinge with oil to separate the surfaces.
  • Competative cycling - cyclists crouch to reduce their surface area and reduce air resistance.
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15
Q

What is the name of the upwards force which keeps the wrecking ball in place?

A

Tension

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16
Q

What is the name of the force which acts upwards in this diagram?

A

Reaction Force

17
Q

What are the units of acceleration?

A

Metres per second squared (ms-2)

18
Q

If I know an objects mass and the acceleration, how do I calculate the force which caused the acceleration?

A

F = ma

19
Q

What is the name of the missing force?

A

Thrust

20
Q

Calculate resultant force

A

400 N to the right

21
Q

This is a Newton Pairs question.

When walking, your shoe exerts a force on the ground. What is the reaction force to this?

A

The reaction force is the force of the ground pushing back up on the shoe.

22
Q

A poop is dropped from rest out of a plane. It is initally accelerates, but eventually travels at a constant speed. What is the name of this speed?

A

Terminal Velocity

23
Q

What is the name of the force acting downwards as the apple falls from the tree?

A

Weight
(DO NOT SAY GRAVITY!!!!)

24
Q

State Newton’s first law of motion.

A

When balanced forces (or no forces) act on an object, it remains at rest, or continues to move at constant speed in a straight line.

You should be able to regurgitate this definition.

25
Q

State Newton’s second law of motion.

A

The acceleration of an object depends on both the unbalanced force applied and its mass.
AKA - F = ma

You should be able to regurgitate this definition.

26
Q

State Newton’s third law of motion.

A

Every action force has an equal and opposite reaction force.

You should be able to regurgitate this definition.

27
Q

Explain why we use seatbelts using Newton’s laws of motion.

A
  • When a car crashes, the car stops, but the people in the car continue forwards at a steady speed (Newton’s I Law).
  • The seatbelt provides an unbalanced force to bring you to a stop safely (Newton’s II Law).
28
Q

Explain why we use airbags, using Newton’s laws of motion.

A
  • Using an airbag increases the time taken to bring you to rest.
  • This decreases the deceleration
  • A smaller deceleration means a smaller force (Newton II Law - F= ma)
29
Q

How does air resistance change with the speed of an object?

A

Air resistance increases with speed.

The faster you go, the more air resistance you experience.

30
Q

What is the name of the missing force?

A

Air Resistance

31
Q

When an object is travelling at terminal velocity, what can you say about the objects weight and the air resistance?

A

At terminal velocity, weight and air resistance are balanced.

KA S3 Physics (5 decks)

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