# P2.1 and 2

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What is the rule of force between objects?
Forces measured in Newtons (N). Objects always exert equal and opposite forces on each other.
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What is a resultant force?
The single force that would have the effect on the object as all of the original forces acting together.
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What happens when a resultant force on an objects is zero?
If @ rest = stay at rest. If moving = It will carry on moving at the same speed & direction
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What happens when a resultant force on an objects is not zero?
There will be an acceleration in the direction of the force. @ Rest = accelerate in resultant force = direction. Moving in same direction as resultant force = accelerate in that direction. Object moving in opposite direction to the resultant force =
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What is the equation for resultant force?
F = m x a Resultant force (N) = mass (kg) x acceleration (m/s to the power of 2)
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What is acceleration?
A change in velocity. An object can change in direction even @ a constant speed. Resultant force is needed for an object to change in direction.
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What is the resultant force on a car travelling at a steady speed on a straight horizontal road?
Zero. The driving forces are equal and opposite of the frictional forces.
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What is the stopping distance?
The distance travelled during the driver’s reaction time + distance travelled under the braking force
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How can the thinking distance and braking distance be increased?
By alcohol or drugs. Poorly maintained roads or adverse weather conditions. The condition of the car (worn tyres or brakes).
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What is the equation acceleration due to gravity?
W = m x g Weight in Newtons (N) = mass (kg) x acceleration due to gravity in m/s squared
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What happens when an object falls through a fluid?
fluid exerts drag force on object resisting its motion. The faster the object falls, the bigger the drag force becomes, until equal to weight of object. The resultant force now = 0. stops acc., moves @ constant velocity = terminal velocity
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What happens when an object falls freely?
The resultant force acting on it is the force of gravity. It will make an object close to the Earth’s surface accelerate at about 10m/s squared.
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What is an elastic object?
One that regains its original shape when the forces deforming it are removed
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What is Hooke’s law?
This states that the extension is directly proportional to the force applied, provided the limit of proportionality is not exceeded
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What does a straight line passes through the origin for a graph of extension against force tell us?
That the extension is directly proportional to the force applied. If we apply too big a force, the line begins to curve because we have exceeded the limit of proportionality.
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What is Hooke’s Law as an equation?
F = k x e Force (N) = spring constant of the spring in newtons per metre (N/m) x extension in metres (m)
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Give three points on springs
Stiffer spring = greater spring constant. When an elastic object is stretched, work is done. This is stored as elastic potential energy in the object. When the stretching force is removed, this stored energy is released
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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. Reducing the air resistance by making the vehicle more streamlined (e.g. fitting a wind deflector) also improves fuel economy.
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What happens when the brakes are applied too harshly?
The vehicle skids when the wheels lock and slide along the road surface, increasing the stopping distance.
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What are Anti-skid surfaces used for?
To reduce or prevent skidding. They are rougher than normal road surfaces, increasing the friction between vehicle tyres and the road. They are used in places where drivers are likely to brake, such as near traffic lights and road junctions
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How do you calculate acceleration
a = v - u / t
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What is speed in metres?
Speed(m/s) = distance (m) / time (s)
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What does a horizontal line on a velocity time graph represent?
The acceleration is 0 = object travelling at steady/constant speed
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What does a positive or negative line represent on a velocity-time graph?
Positive = accelerating. Negative = decelerating
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## Other cards in this set

### Card 2

#### Front

What is a resultant force?

#### Back

The single force that would have the effect on the object as all of the original forces acting together.

### Card 3

#### Front

What happens when a resultant force on an objects is zero?

### Card 4

#### Front

What happens when a resultant force on an objects is not zero?

### Card 5

#### Front

What is the equation for resultant force?