When two objects interact, they put forces on each other. Describe the size and directions of these forces.
Forces occur when there is an interaction between two objects. These forces always happen in pairs – when one object exerts a force on another, it always experiences a force in return.
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What is a resultant force? Give an example calculation.
overall force on an object. e.g. car driving force = 1000N, air resistance 600N, result is 1000N-600N = 400N
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If an object has a resultant force acting on it, describe the 3 different things that may happen to the object
Accelerate, decelerate and/or change direction.
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If an object has no resultant force acting on it (forces are balanced) what happens to it if a. It is at rest? b. It is already moving
a.) stays where it is, b.) velocity remains the same
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What does the gradient of a distance-time graph tell you?
The speed of the object
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What does the gradient of a speed-time graph tell you?
The rate of acceleration
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What does the area underneath a speed-time graph tell you?
Distance travelled in the selected time interval
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What is velocity?
Speed in a direction
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What is friction and which direction does it always act in?
Friction is an opposing force caused by drag on a surface or in a fluid, and acts in the oppposite direction to the movement.
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What is air resistance and which direction does it always act in? How can you increase it?
Air resistance is the resistive force encounter when pushing through a fluid like air, which opposes the movement (opposite direction)
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What is the stopping distance of a vehicle?
This is the sum of the thinking distance and the braking distance
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When a vehicle is braking, what is the energy transformation?
Kinetic energy is turning into heat energy.
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When a vehicle is braking, the brakes are doing work on the car, what does ‘work done’ mean?
It means the amount of kinetic energy transferred
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What is thinking distance?
The distance travelled during the driver's reaction time
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What factors affect the thinking distance of a car and why?
How fast you are going, and how dopey (tiredness, drugs, alcohol and careless attitude)
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What is braking distance?
The distance the car travels under the braking force
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What factors effect braking distance of a car and why?
Speed (how fast you are going), Brakes (good condition or worn), Tyres (deeper tred gives off better grip), and Grip (quality of the road surafce + weather conditions)
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When an object (e.g. a parachutist) falls thought the air, what forces are acting on it?
weight (mass * gravity) and air resistance
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What is the force due to gravity called?
weight
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What is g and what value does it have on Earth?
"g" represents the strength of the gravity. On Earth "g" = 10N/kg
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What is the difference between mass and weight?
Weight is the force of gravity acting on a mass, and mass is the amount of stuff measured in kg.
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As a parachutist falls through the air, describe the forces acting on them, how they change and how this effects the parachutist’s motion.
His weight is pulling him down, air resistance is pushing him up. With no parachute open he will accelerate up to a terminal velocity of 120mph. Once he pulls his parachute, air resistance increases and he will slow to a constant 15mph.
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Sketch a velocity time graph for a parachutist from when they jump out of the plane to when they reach terminal velocity
See below
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What are the conditions for terminal velocity?
When the friction caused by falling through a substance (like air) equals the accelerating force
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What are all forces measured in?
Newtons
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When an object is stretched, what type of energy is stored?
Elastic Potential energy
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What is Hooke’s Law? Sketch a force-extension graph for a material that obeys Hooke’s Law
When an elastic object - such as a spring - is stretched, the increased length is called its extension. The extension of an elastic object is directly proportional to the force applied to it: F = k × e. See below for graph.
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When stretching a material, what is the limit of proportionality and what happens after it?
The limit of proportionality is the point up to which an object stretches in proportion to the force applied. After this point, the internal stability of the object is broken and the rate of extension increases.
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What is an elastic material?
An elastic material is one that has the ability to stretch or shrink when force is applied and return to its original size/shape afterwards by releasing elastic potential energy stored within it by the original force.
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Other cards in this set
Card 2
Front
What is a resultant force? Give an example calculation.
Back
overall force on an object. e.g. car driving force = 1000N, air resistance 600N, result is 1000N-600N = 400N
Card 3
Front
If an object has a resultant force acting on it, describe the 3 different things that may happen to the object
Back
Card 4
Front
If an object has no resultant force acting on it (forces are balanced) what happens to it if a. It is at rest? b. It is already moving
Back
Card 5
Front
What does the gradient of a distance-time graph tell you?
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