AS Physics - Forces and Motion Key Words

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Speed
Distance per unit time
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Displacement
Distance moved in a particular direction from a reference point
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Velocity
Displacement per unit time
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Acceleration
Change in velocity per unit time
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Thinking distance
The distance a vehicle travels between the driver seeing a hazard and applying the breaks
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Braking distance
The distance a car travels between the brakes being applied and coming to rest
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Stopping distance
The sum of thinking and braking distance
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Resultant force
A single force which has the same effect as the sum of all the forces acting on a body.
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Newton
1 Newton is the force required to accelerate a mass of 1kg at 1ms^-1
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Equilibrium
An object will be in (linear) equilibrium if the resultant force acting on it is zero. This means that the object will be travelling at a constant velocity or will be stationary.
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Moment
The turning effect of a force. It is the product of a force and the perpendicular distance of its line of action from the point or axis.
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Couple
A pair of equal and opposite forces whose line of action are separated. This leads to pure rotation.
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Turning moment (torque) due to a couple
The product of one of the forces and the distance between the two forces.
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Centre of mass
The single point at which all of the mass of an object can be assumed to be situated.
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Centre of gravity
The single point through which the entire weight of an object can be thought to act.
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Density
Mass per unit volume
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Archimedes Principle
When an object is floating or submerged in a fluid, the upthrust of the fluid on that object is equal to the weight of the fluid displaced by the object.
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Pressure
The force per unit area at right angles to the area
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Work
The product of force and distance moved in the direction of the force.
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Joule
1 joule is the work done when a force of 1N is moved through a distance of 1m
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Closed system
Any system where all the energy transfers are accounted for.
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Principle of Conservation of Energy
The total energy in a closed system remains constant. Energy cannot be created or destroyed; it can only be transferred from one form to another.
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Gravitational potential energy
The energy an object has by virtue of its position in a gravitational field.
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Kinetic energy
The energy an object has due to its motion.
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Power
The rate of energy transfer.
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Efficiency
The useful energy output divided by the total energy input.
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Elastic deformation
When a material returns to its original shape/length after having forces applied.
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Plastic deformation
When a material does not return to its original shape/length after having forces applied.
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Hooke's Law
A law which states that the extension of an object is proportional to the force that causes it, provided the elastic limit is not exceeded.
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Tensile stress
Force per unit cross sectional area.
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Tensile strain
Extension per unit (original) length.
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Young modulus
The tensile stress of an object divided by the tensile strain of that object.
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Ductile
Can be drawn into wires and will show plastic deformation under tensile stress before breaking.
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Malleable
Can be hammered or beaten into flat sheets and will show extensive plastic deformation when subjected to compressive forces.
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Brittle
Will break with little or no plastic deformation.
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Hard
Will resist plastic deformation by surface indentation or scratching.
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Stiffness
The ability of a material to resist tensile forces.
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Polymeric
Made of long chains of molecules called polymers.
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Ultimate tensile strength
The maximum stress that a material can withstand before it breaks.
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Newton's First Law
A body will remain at rest or move in a straight line at a constant velocity unless acted on by a non-zero resultant force.
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Newton's Second Law
The resultant force of an object is proportional to the rate of change of momentum of the object.
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Newton's Third Law
If object A exerts a force on object B, then object B will exert an equal and opposite force on object A.
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Momentum
The product of mass and velocity
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Conservation of momentum
When two or more objects interact, the total momentum before the interaction will be equal to the total momentum after the interaction, provided that no external force acts on the system.
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Impulse
The product of force and the time in which this force acts.
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Elastic collision
A collision in which the kinetic energy of the system is conserved.
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Inelastic collision
A collision in which the kinetic energy of the system is not conserved. Some of the energy will be transferred to thermal energy.
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Other cards in this set

Card 2

Front

Distance moved in a particular direction from a reference point

Back

Displacement

Card 3

Front

Displacement per unit time

Back

Preview of the back of card 3

Card 4

Front

Change in velocity per unit time

Back

Preview of the back of card 4

Card 5

Front

The distance a vehicle travels between the driver seeing a hazard and applying the breaks

Back

Preview of the back of card 5
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