# Forces

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• Created by: KAustria
• Created on: 03-05-14 20:31
What is term used to describe when forces exert equal and opposite forces?
Action and reaction
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What is the unit used to measure Forces?
Newtons, N
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In what direction does the force of weight always act?
Downwards - Towards the centre of the Earth
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What is the name of the single force that would have the same effect o the object as all the original forces acting together?
Resultant Force
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When the resultant force is 0 what is the state of an object when it is at rest, and when it is moving?
When it is at rest the object remains stationary. When it is moving the object is moving at a steady speed.
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What happens when the resultant force of an object is not 0?
The object will accelerate to the direction of the force
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What happens to an object moving in the opposite direction to the resultant force?
It will decelerate
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What is deceleration?
Negative acceleration
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What is the resultant force of an 4 N force and a 3N force acting in the same direction?
7N
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What is Acceleration?
The change in Velocity, m/s^2
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What is the equation used to find the resultant force?
F= ma
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In terms of acceleration : the bigger the mass of the object the [BLANK] the force needed to give it a particular acceleration
Bigger
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What happens to the accleeration of an object as the resultant force on it decreases?
Acceleration decreases
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What has happened to the forces of a vehicle which is travelling at a steady speed?
The driving force is equal to the frictional forces
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What is stopping distance?
Thinking Distance (reaction time) + Braking Distance (braking force)
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What are the 3 main factors which can increase a vehicles braking distance?
1. Poorly maintained roads 2. bad weather conditions 3. Conditions of cars
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What is the resultant force of an object which is falling freely?
Gravity
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How fast does a object accelerate due to the force of gravity?
10m/s^2
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What is the force of gravity also known as?
Weight
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What is the equation used to find weight?
W = m x g (acceleration due to gravity)
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If an object is not falling and it is on what can g (from w=mg) stand for?
Gravitational field strength
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What is the force called when a object travels through a fluid and resists its motion?
Drag force
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Define terminal velocity
Terminal Velocity is when resistive force is equal to driving force/weight that the object has a resultant force of 0
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Why does an object in a fluid initially accelerate?
The weight of the object is greater than the drag forces
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Objects that regain their original shape when the forces deforming it are removed are known as what?
Elastic objects
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What is an inelastic object?
An object tat doesn't regain it's original shape when the weight deforming it is removed.
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How doe we know if an extension is directly proportional to the force applied?
If we plot a graph of extension to the force applied for a spring, we obtain a straight line that passes through the origin
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What is called when the a force too big is applied to an object that a curve appears on a graph?
The force applied has exceeded the limit of proportionality
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What is Hooke's law?
Hooke Law states that the extension is directly proportional to the force applied, provided the limit of proportionality is not exceeded.
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What is the equation for Hooke's law?
F(orce applied, N) = k (the srping constant, N/m) x e(xtension in metres, m)
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What is fuel economy?
Reducing the speed of a vehicle reduces the amount of fuel it uses to travel a particular distance
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How could you reduce air resitance?
Making a car more streamlined
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How are motorists discouraged form speeding?
By using speed cameras
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When a vehicle is travelling along a straight road at a steady seed what can you say about the engine and the air resistance?
Air resistance and the engine force is equal
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Why do cars have a top speed?
The faster a car travels, the greater the air resistance acting against it. Until eventually the two forces are equal and a car is travelling at a steady speed.
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If a spring is stiff what is its spring constant like?
Greater spring constant
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What is the energy transferred called to and elastic object when it is stretched?
Elastic Potential energy
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## Other cards in this set

### Card 2

#### Front

What is the unit used to measure Forces?

Newtons, N

### Card 3

#### Front

In what direction does the force of weight always act?

### Card 4

#### Front

What is the name of the single force that would have the same effect o the object as all the original forces acting together?

### Card 5

#### Front

When the resultant force is 0 what is the state of an object when it is at rest, and when it is moving?