 # 1 Forces and Motion – Part A “Units”

### Aims…

1.1 use the following units: kilogram (kg), metre (m), metre/second (m/s),metre/second2 (m/s2), newton (N), second (s) and newton/kilogram (N/kg)

1.2P use the following units: newton metre (Nm), kilogram metre/second
(kg m/s)  (Triple)

### General Ideas…

A physical quantity is something that can be measured. For any measurement, the unit being used must be stated to give an understanding of the scale of the measurement.

For example, distance can be measured in kilometres or in miles. They are similar, but not the same and it is important to identify which was used for the measurement, to know how far the distance actually is.

Système Internationale d’Unités

The units that scientists use all over the world are standardised in the Système Internationale d’Unités – SI units. It is important to remember these six fundamental (or ‘base’) units of measurement:

There are many quantities scientists measure that come from the base units. These derived units are very useful to quote as measurements, but they are not fundamental as they come from fundamental units.

For example, frequency is the number of times something happens per unit of time.

This is a useful quantity, but it is a division into the time unit.

The standard unit for frequency is considering the number ‘per second‘, which is called ‘hertz, Hz’, but this comes from the fundamental unit ‘second‘.

 Name Unit Abbreviation Frequency hertz Hz Force newton N Energy joule J Power watt W Pressure pascal Pa Electric charge coulomb C Work Done or Work Nm or J W Gravity or acceleration Nkg-1ms-2 g or a Momentum kgms-1 p

### Resources….

Use this PowerPoint for a quick review… 1 Force and Motion Part A Units ## 1 Forces and Motion – Part B “Motion”

Aims…
1.3 plot and interpret distance–time graphs
1.7 plot and interpret velocity–time graphs
1.8 determine acceleration from the gradient of a velocity–time graph
1.9 determine the distance travelled from the area between a velocity–time graph and the time axis.
1.4 know and use the relationship between average speed, distance moved and time:  average speed = distance moved/time taken
1.5 practical: investigate …

## 1 Forces and Motion – Part C1 “Shape and Hookes Law”

Aims…
1.11 describe the effects of forces between bodies such as changes in speed, shape or direction
1.12 identify different types of force such as gravitational or electrostatic
1.13 understand how vector quantities differ from scalar quantities
1.14 understand that force is a vector quantity
1.15 calculate the resultant force of forces that act along a line
1.16 know that friction …

## 1 Forces and Motion – Part C2a “Movement F = ma, Terminal V, Stopping Distances”

Aims…
1.17 know and use the relationship between unbalanced force, mass and acceleration:
force = mass × acceleration   OR   F = m × a
1.18 know and use the relationship between weight, mass and gravitational field strength:
weight = mass × gravitational field strength     OR    W = m × g
1.19 know that the stopping distance of a …

## 1 Forces and Motion – Part C2b “Momentum and Moments”

Aims… (Triple Only)
1.25P know and use the relationship between momentum, mass and velocity:
momentum = mass × velocity      OR    p = mv
1.26P use the idea of momentum to explain safety features
1.27P use the conservation of momentum to calculate the mass, velocity or momentum of objects
1.28P use the relationship between force, change in momentum and time taken:
force …