# Unit One Definitions

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The word

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Definition of the word from OCR book

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- Created on: 09-12-14 12:35

Acceleration

The rate of change of velocity, measured in metres per second squared (ms^-2). A vector quantity.

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Acceleration of free fall

The acceleration of a body falling under gravity. On earth it has the value of 9.81ms^-2

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Area

A physical quantity representing the size of part of a surface. Always measured in metres ^2

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Average speed

A measure of the total distance travelled in a unit time.

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Braking Distance

The distance a vehicle travels while decelerating to a stop.

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Brittle

A material that distorts very little even when subject to a large stress and does not exhibit any plastic deformation; concrete

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Centre of gravity

The point at which the entire weight of an object can act.

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Components of a vector

The results from resolving a single vector into a horizontal and vertical parts.

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Compressive force

Two or more forces that have the effect of reducing the volume of the object on which they are acting, or reducing the length of a spring.

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Conservation of energy

Physical law stating that energy cannot be created or destroyed; just transformed from one form to another. This is a closed system.

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Couple

Two forces that are equal and opposite to each other but not in the same straight line.

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Crumple Zone

An area of a vechile designed to increase the distance over which the vehicle decelerates and so reduce the average force acting.

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Density

The mass per unit volume, measured in kilograms per cubic metre; kgm^-3

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Displacement

The distrance travelled in a particular direction, measured in metres (vector quantity)

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Displacement-time graph

A motion graph showing displacement against time for a given body.

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Distance

How far one position is from another, measured in metres

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Drag

The resistive force that acts on a body when it moves through a fluid.

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Drag coefficient

A characteristic that determines the amount of drag that acts on an object.

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Ductile

Materials that have a large plastic region (therefore they can be drawn into wire for example copper.

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Dynamo

A device that converts kinetic energy into electrical energy.

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Efficiency

The ratio of useful output energy to total input energy. efficiency = useful energy/total energy supplied

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Elastic Deformation

The object will return to its original shape when the deforming force is removed.

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Elastic limit

The point at which elastic deformation becomes plastic deformation

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Elastic potential energy

The energy stored in a stretched or compressed object (like a spring) measured in joules

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Energy

The ability to do work, measured in joules

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Equations of Motion

The equations used to describe displacement, acceleration, intial velocity, final velocity and time when a body undergoes a CONSTANT acceleration.

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Equilibrium

When there is zero resultant force acting on an object.

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Extension

The change in length of an object when subjectedd to tension, measured in metres (m).

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Fluid

A material that can flow from one place to another (liquid and gases).

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Force

A push or pull on an object, measured in newtons (N)

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Force Constant

The constant of proportionality in Hooke's Law, measured in newtons per metre (Nm^-1)

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Free fall

When an object is accelerating under gravity.

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Global Positioning System

A network of satellites used to determine an object's position on the earth's surface. Uses trilateration and used for navigation.

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Gradient of a Graph

The change in y-axis over the change in x-axis (y2-y1/x2-x1)

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Gravitational Force

The force due to a gravitational field acting on an object's mass.

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Gravitational Potential Energy

The energy stored in an object (the work an onject can do) by virtue of the object being in a gravitational field, measured in joules. (KE=GPE) (GPE=mgh)

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Hooke's Law

The extension of an elastic body is proportional to the force that causes it.

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Instantaneous Speed

The speed of an object at a given moment in time

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Joule

(1J = 1Nm) Unit of energy. 1J is the work done when a force of 1N moves its point of application 1m in the direction of the force.

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Kilowatt

Unit of power (1kW=1000W)

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Kinetic Energy

The work an object can do by virtue of its speed, measured in joules. KE=1/2mv^2

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Moment of a Force

The turning effect due to a single force, calculated from the force multiplied by the perpendicular distance from a given point, measure in Nm

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Newton

Unit of a force. 1N is the force which gives a mass of 1kg an acceleration of 1ms^-2

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Plastic deformation

The object will not return to its original shape when the deforming force is removed, it becomes permanently distorted.

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Polymeric Material

A material made of many smaller molecules bonded together, often making tangled long chains. These materials often exhibit very large strains.

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Potential Energy

A form of stored energy.

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Power

The rate of doing work, measured in Watts (Js^-1)

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Pressure

Force per unit area, measured in Pascals (Pa = Nm^-1)

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Principle of Moments

For a body to be in rotational equilibrium, the sum of the clockwise moments equals the sum of the anti-clockwise moments.

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Resolution of Vectors

Splitting a vector into horizontal and vertical components.

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Resultant Force

The overall force when two or more forces are combined.

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Resultant Velocity

The overall velocity when two or more velocities are combined.

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Scalar

A physical property with magnitude (size) but not direction.

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Speed

The distance travelled per unit time, measured in metre per second (ms^-1)

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Spring Constant

force per unit extension

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Stopping distance

The sum of the thinking distance and the braking distance. The total distance required to stop a vehicle from seeing the need to stop to the vehicle becoming stationary.

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Stress

F/A - The force per unit cross sectional area (Pa)

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Strain

x/L - The extension per unit length.

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Tensile Force

Usually two equal and opposite forces acting on a wire in order to stretch it. When both forces have th evalue T, the tensile force is T not 2T

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Tensile stress

The tensile force per unit cross sectional area

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Terminal Velocity

The velocity at which an object's drag equals it's accelerating force. Therefore there is no resultant force and zero acceleration.

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Thinking distance

The distance travelled from seeing the need to stop to applying the brakes.

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Thrust

A type of force due to an engine.

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Torque

The turning effect due to a couple, meausured in Nm

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Triangle of Forces

If three forces acting at a point can be represented by the sides of a triangle, the forces are in equilibrium.

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Turning Forces

One or more forces that if unbalanced will cause rotation.

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Ultimate Tensile Strength

The maximum tensile force that can be applied to an object before it breaks.

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Ultimate Tensile Stress

The maximum stress that can be applied to an object before it breaks.

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Upthrust

A force on an object due to a deifference in pressure when immersed in a fluid.

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Vector

A physical quantity that has both magnitude (size) and direction. For example velocity

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Velocity

The displacement per unit time, measure in metres per second.

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Velocity-time graph

A motion graph showing velocity against time for a given body.

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Volume

A physical quantity representing how much 3D space an object occupies, measured in metres cubed.

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Watt

Unit of power

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Weight

The gravitational force on a body, measure in newtons. (W = mg)

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Work

The product of force and the distance moved in the direction of the force, it can also be considered as the energy converted from one form into another, measured in Joules. W = Fd

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Young's Modulas

The ratio between stress and strain. (YM = stress/ strain or FL/xA)

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## Other cards in this set

### Card 2

#### Front

The acceleration of a body falling under gravity. On earth it has the value of 9.81ms^-2

#### Back

Acceleration of free fall

### Card 3

#### Front

A physical quantity representing the size of part of a surface. Always measured in metres ^2

#### Back

### Card 4

#### Front

A measure of the total distance travelled in a unit time.

#### Back

### Card 5

#### Front

The distance a vehicle travels while decelerating to a stop.

#### Back

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