define scalar and vector quantities and give examples;

Scalar: Magnitude without direction

Density, volume, temperature etc

Vector: A quantity that has (both) magnitude / size and direction

acceleration, displacement and weight etc

define displacement

Displacement = (net) distance moved in a particular direction.

define instantaneous speed

Instantaneous speed = speed of a body at a specific instance or at a specific point

define average speed

distance travelled / time taken

define velocity

speed in a given direction

define acceleration

Acceleration is the rate of change of velocity (gradient of a velocity vs time graph, change in velocity/time taken)

Define average velocity

(net) displacement / time taken

define the newton;

The (net) force which gives a mass of 1kg an acceleration of 1 ms^{-2}

define the torque of a couple;

**one of forces × perpendicular distance (between forces) **

(Not force x perpendicular distance)

define the moment of force;

moment = force x perpendicular distance from pivot / axis / point

define thinking distance

Thinking distance: The **distance** travelled (by the car) from when the driver sees a problem and the brakes are applied

Define braking **distance **

The **distance** travelled (by the car) whilst the brakes are applied and the car stops

define stopping distance

stopping distance: Thinking distance + braking distance. The total distance travelled in the interval between a driver spotting a hazard, and the vehicle coming to a complete stop.

define work done by a force;

work done = force x distance moved in the direction of the force

define the joule;

Energy required to move a weight of 1N (through) a distance of 1 m

define power

The rate at which work is done:

Power = Work done / Time

OR

Power = Energy / Time

Define the Watt

Power required to move 1N through a distance of 1m in 1 sec (Rate of doing work)

Define Stress

force/(cross-sectional) area

Define Strain

extension/original length

Define Young's modulus

Young modulus = stress/strain / Young modulus is equal to the gradient from stress-strain graph (in the linear region)

Define ultimate tensile strength

Ultimate tensile strength = Maximum stress material can withstand (before fracture)

define the term elastic deformation

Elastic extension (or compression) is proportional to force (as long as elastic limit is not exceeded)

define plastic deformation of a material

Plastic: Material does not return to original length / shape/ size (is permanently deformed / longer) when the force / stress is removed.

Define density

Density = mass/volume or mass per (unit) volume

Derive the equations of motion for constant

acceleration in a straight line from a velocity

against time graph;

Area of triangle = ½ (v-u) t [(v-u) = at]

= ½ at^{2}

Area of rectangle = ut add the two together

Apply the definition of work done to derive the equation for the change in gravitational

potential energy;

Work done = force x distance

Force = mass x acceleration

Weight = mass x gravitational field strength

G.P.E. = m x g x h

apply the equations of constant acceleration to describe and explain the motion of an object due to a uniform velocity in one direction and a constant acceleration in a perpendicular direction

With a uniform velocity in one direction the distance travelled per unit time will remain constant

s = ut + ½at^{2}

For a = 0

s = ut which is linearly proportional to "t"

With a constant acceleration in another direction the distance travelled per unit time in that direction increases.

s = ut + ½at^{2} which is not linearly proportional to "t"

This means that the object traces a parabollic path.

If **work** is done on a system, what can we say about transfer of energy in that system.

If work is done energy must be transfered from one type to another. The total amount of energy transferred into other forms is **equal** to the work done

describe an experiment to determine the

acceleration of free fall g using a falling body;

**Measurements:**

1) Height (distance)

2) Time (of fall)

**Equipment**

1) Ruler/tape (measure)

2) Stop watch/timer/clock/video

**Calculation:**

g = 2s/t^{2} or g = twice the gradient of s-t^{2} graph

**Why is this not accurate?**

air resistance / drag

parallax (landing time)

starting/stopping the clock

**Derivation of g = 2s/t ^{2}**

s=ut+½at^{2} (ut=0),

s = ½at^{2},

a=2s/t^{2}

For a falling body a = g, so g = 2s/t2

Describe the motion of bodies falling in a

uniform gravitational field with drag;

1) Initially the body has no speed. The resultant force acting on it is 9.81N/kg and it is accelerating at 9.81m/s^{2}. Because the body has no velocity, air resistance is zero.

2) Then as speed increases, air resistance increases, so the** resultant **force is now less than 9.81N/kg and therefore its acceleration is decreasing.

3) Eventually the object will reach a speed where the force of air resistance balances the force of gravity. At this point there is no acceleration, we say the object has reached **terminal velocity**.