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gcse triple science physics > Topic 5: Forces > Flashcards

Topic 5: Forces Flashcards

1
Q

What is a force?

A

A force is a push or pull object that is caused by it interacting with something

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2
Q

What is a non-contact force?

A

When the objects do not need to be touching for the force to act

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3
Q

What is a contact force?

A

When two objects have to be touching for the force to act

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4
Q

What is an interaction pair?

A
  • an interaction pair of forces that are equal and opposite and act on two interacting objects
  • there is a force on both objects when two objects interact (basically Newton’s Third Law)
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5
Q

What are vector quantities? Give some examples

A

Vector quantities have a magnitude and a direction e.g. force, velocity, displacement, acceleration, momentum etc.

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6
Q

What are scalar quantities? Give some examples

A

Scalar quantities have only magnitude and no direction e.g. speed, distance, mass, temperature, time, etc.

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7
Q

Describe how vectors are usually presented

A

Vectors are usually represented by an arrow - the length of the arrow shows the magnitude, and the direction of the arrow shows the direction of the quantity

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8
Q

What does friction do?

A

If an object has no force propelling it along, it will always slow down and stop because of friction

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9
Q

How does friction work?

A

Friction always acts in the opposite direction to movement

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10
Q

Why does the driving force need to balance the frictional forces?

A

To travel at steady speed

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11
Q

When will friction occur?

A

You get friction between two surfaces in contact, or when an object passes through a fluid (drag)

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12
Q

What does terminal velocity depend on?

A

Shape and area

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13
Q

What is gravity and how does it affect falling objects?

A

Gravity is the accelerating force acting on all objects and it would make them all fall at the same rate if it wasn’t for air resistance

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14
Q

How does gravity affect falling objects on the moon?

A

On the moon where there’s no air, hamsters and feathers dropped simultaneously will hit the ground together

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15
Q

How does air resistance on earth affect falling objects?

A

Air resistance causes objects to fall at different speeds

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16
Q

What is terminal velocity determined by?

A

The terminal velocity of any object is determined by its drag in comparison to its weight

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17
Q

What does the frictional force depend on?

A

Shape and area

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18
Q

What does it mean when objects fall through fluids? What do they reach?

A

Terminal velocity

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19
Q

What happens to falling objects when they first set off?

A

The force of gravity is much more than the frictional force slowing it down, so it accelerates

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20
Q

What happens to friction as speed increases?

A

As speed increases, the friction builds up

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21
Q

As friction builds up when speed increases, how does this affect the acceleration of an object?

A

This gradually reduces the acceleration until the frictional force is equal to the accelerating force, so the resultant force is zero

22
Q

What happens to drag when speed increases?

A

Drag increases as speed increases

23
Q

What is drag? Give an example

A

Drag is the resistance you get in a fluid (a gas or a liquid) e.g. air resistance

24
Q

What is the most important factor for reducing drag?

A

Keeping the shape of the object streamlined - where the object is designed to allow fluid to flow easily across it, reducing drag
(Parachutes work in the opposite way - they want as much drag as they can get)

25
Give an example where frictional forces from fluids always increases with speed
- a car has much more friction to work against when travelling at 70 mph compared to 30 mph - so at 70 mph, the engine has to work more harder just to maintain a steady speed
26
What is moment?
The rotational or turning effect of a force
27
How does the distance between the pivot and where the force is being exerted, affect the force itself?
The closer the force is being applied to the pivot, the greater the force applied needs to be
28
What do levers do?
Transmit the turning effect of a force
29
What does the gear system allow to do?
Gears transmit turning effects The gear system allows the turning effect of the engine to be transmitted to the wheels Gears turn in opposite directions
30
What is pressure
Pressure is the force per unit of area
31
What is the perpendicular force?
Component of the force which is at right angles to the surface it's colliding with
32
Describe how an object sinks
- when an object is submerged into the water - forces will be exerted onto it from different directions - there is a resultant force pushing the object upwards known as upthrust - if the weight of the object is greater than upthrust, the object will sink
33
Describe how an object floats
- when an object is submerged into the water - forces will be exerted onto it from different directions - there is a resultant force pushing the object upwards known as upthrust - if upthrust is greater than the weight of the object, the object will float
34
How does the density of the object affect whether the object can float or not?
If the object's density is greater than the density of the liquid, the object will sink If the density of the liquid is greater than the object's density, the object will float
35
Describe how pressure is affected when really high up in the air
The density of the gas particles is highest near the earth's surface, so the pressure gets smaller the further away from the earth When in the air, there are fewer particles and weight will be smaller Air is thinner the higher up you are
36
How is terminal velocity reached?
- there's a maximum forward force - as speed increases, air resistance increases - forward force = air resistance - resultant force equals zero - terminal velocity reached
37
How Is terminal velocity affected when high up in the air?
- at high altitude, the air is thinner - meaning a falling object would accelerate for longer periods of time as there's less air resistance - air resistance then increases - reaches a higher terminal velocity
38
State Newton's first law
A resultant force is required to change the motion of an object
39
Using Newton's first law, explain what happens when an object remains stationary
If there's no resultant force acting on a stationary object, the object will remain stationary The motion won't change
40
Using Newton's first law, explain what happens when an object is moving
If there's no resultant force on a moving object, it carries on moving at the same velocity Motion wont change
41
State Newton's second law
Non-zero resultant forces act on an object, then it will cause the object to accelerate The size of the resultant force is directly proportional to the acceleration it causes
42
What is inertia?
The tendency for the motion of an object to remain unchanged
43
State Newton's Third law
When two objects interact, the forces they exert on each other are equal and opposite
44
What is stopping distance?
The minimum distance required to stop a vehicle in an emergency Stopping distance = Thinking distance + Braking distance
45
What is thinking distance?
How far the car travels during the driver's reaction time
46
What is the thinking distance affected by?
- speed - reaction time - linking to being tired, drunk etc. All increases reaction time
47
What is braking distance?
Distance taken to stop under the braking force
48
What is braking distance affected by?
Speed and mass 1. Condition/ quality of the brakes: worn or faulty - wont slow the car as quickly, it'll travel further before it stops 2. If the road is wet or icy, there's less friction between the tyres and the road - can cause the car to skid All increases reaction time
49
What is the conservation of momentum principle?
In a closed system, total momentum before = total momentum after
50
Describe what happens to the momentum of people involved in a car crash
For the people inside the car, their momentum is going to decrease to 0 almost instantly They will then experience a huge force which could cause injury
51
How can we reduce the chance of injury when in a car crash and how can it be achieved?
You can spread the change in momentum over a longer period of time as it will reduce the force they experience - less likely to get injured Can be achieved through air bags, seat belts and crumple zones as they all increase the time taken for momentum to be lost - lower force

gcse triple science physics (9 decks)

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