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Physics > Forces > Flashcards

Forces Flashcards

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1
Q

What do objects exert onto each other?

A

Equal and opposite forces

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2
Q

In what direction does the force of weight always act?

A

Downwards or towards the centre of gravity

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3
Q

Do most objects have more than one force acting on them?

A

Yes

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4
Q

What’s the resultant force?

A

The single force that has the same effect as all the forces acting on an object.

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5
Q

What’s the unit of resultant force?

A

Newton

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6
Q

If an object is accelerating there must be a ……. Acting on it?

A

Resultant

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7
Q

If an object is accelerating it can be what?

A

Speeding up
Slowing down
Changing direction

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8
Q

What is the resultant force of a 4N force and 3N force acting in the same direction?

A

7N

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9
Q

What causes acceleration?

A

A resultant force

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10
Q

Define acceleration

A

A change in velocity

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11
Q

How can we find the resultant FORCE?

A

F=ma

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12
Q

The greater the resultant force on an object, the greater it’s …..?

A

Acceleration

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13
Q

What happens to the acceleration of an object as the resultant force on it decreases?

A

Acceleration decreases

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14
Q

What is the resultant force on a car of mass 1000kg if it’s acceleration is 2m/s?

A

2000N

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15
Q

What oppose the driving force of a car?

A

Friction and air resistance

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16
Q

What’s the resultant force on it is zero what’s the vehicle doing?

A

Travelling at a steady speed.

17
Q

Fill in the gap:

The faster the speed of a vehicle, the bigger the __________ needed to stop it.

A

Deceleration

18
Q

What’s the stopping distance?

A

Distance it travels during the thinking distance plus the braking distance
Thinking+braking distance

19
Q

How is the thinking distance increased?

A

Driver tired, drunk or taken drugs

20
Q

The braking distance can be increase by what?

A

Poorly maintained roads
Bad weather
Condition of car
Worn brakes or tyres

21
Q

What’s the relationship between stopping distance, thinking distance and braking distance?

A

Stopping distance = thinking distance + braking distance

22
Q

If an object falls freely , what resultant force is it acting on?

A

Force of gravity

23
Q

The weight of an object is the …?

A

Force of gravity

24
Q

What’s mass and what’s weight?

A

Mass is the amount of matter in an object

Weight is the force of gravity acting on it

25
Q

The terminal velocity of an object is?

A

It’s the velocity it reaches when it is falling in a fluid, the weight is then equal to the drag force on object.

26
Q

Define drag force

A

A force opposing the motion of an object due to fluid flowing past the object as it flows.

27
Q

Why does an object dropped in a fluid initially accelerate?

A

There’s a resultant force acting on it.

28
Q

What eventually happens to an object falling in a fluid?

A

It will reach a terminal velocity because the resultant force becomes 0.

29
Q

What’s an elastic object?

A

An object that regains it’s original shape when the forces deforming it are removed.

30
Q

I we plot a graph of extension against force applied for a spring, we obtain a straight line that passes through the origin what does it tell us?

A

That extension is directly proportional to the force applied.

31
Q

A spring has a constant of 30N/m. If the extension is 0.30m, what is the force applied?

A

9 N

32
Q

How can we tell a spring has exceeded it’s limit of proportionality ?

A

The line on the graph is no longer straight.

33
Q

What does Hooke’s law state?

A

States that the extension is directly proportional to the force applied, provided the limit of proportionality is not exceeded.

34
Q

What to anti skid surfaces do?

A

Increase the friction between a car tyre and road surface.

35
Q

Why does making a vehicle more streamlined improve fuel economy?

A

Less engine force and less power are needed to maintain a certain speed. Therefore less fuel is needed.

36
Q

When a vehicle is travelling along a straight road at a steady speed what can you say about the engine force and the air resistance.

A

The vehicle isn’t accelerating, so the resultant force on it is zero. So the engine force and air resistance are balanced.

37
Q

What are forces measured in?

A

Newtons

Physics (9 decks)

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