# Topic: Challenging Forces

## 1.01 use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second^2(m/s^2), newton (N), second (s) and newton/kilogram(N/kg)

Make sure you are familiar with units for

Mass: kilogram (kg)

Distance: metre (m)

Speed: metre per second (m/s)

Acceleration: metre per second squared (m/s^2)

Force: newton (N)

Time: second (s)

Gravity: newton/kilogram (N/kg)

## 1.03 plot and explain distance-time graphs

A distance time graph has distance on the y axis (usually in metres) and time on the x axis (usually in seconds). The gradient of the line (change in y/ change in x) is the speed. If the line is flat then the object is stationary.

## 1.07 plot and explain velocity-time graphs

on a velocity time graph the velocity-time graph the velocity is on the y axis (usually in m/s) and time is on the x axis (usually in s). If the line is flat then the object is moving at a constant velocity. the gradient of the line is the acceleration. The area under the line is the distance travelled.

## 1.11 describe the effects of forces between bodies such as changes in speed, shape or direction

Forces can act on a body to change the velocity, so the speed, direction or both.

Or forces can change the shape of a body, stretching it squishing it or twisting it.

## 1.12 identify different types of force such as gravitational or electrostatic

different types of forces include:

Gravitational, weight, friction, electrostatic, air resistance (drag), tension (force in a spring), up thrust, lift, thrust

## 1.13 understand how vector quantities differ from scalar quantities

scalars are quantities with only magnitude (size)

vectors are quantities with magnitude (size) and direction

## 1.14 understand that force is a vector quantity

Force has a magnitude measured in (N) but it also has a direction, a push or a pull, up, down, left or right. So force is a vector.

## 1.21 describe the forces acting on falling objects (explain why falling objects reach a terminal velocity)

Initially the only force is weight as drag is proportional to velocity. So the object accelerates downwards. As it accelerates the velocity so the drag increases as well. meaning there is a smaller resultant force downwards so a smaller acceleration. Until the object reaches a speed where the drag is equal to the weight meaning there is no acceleration, this velocity is know as terminal velocity.

## 1.22 practical investigate how extension varies with applied force for helical springs, metal wires and rubber bands

1. Set up your apparatus as shown in the
2. Measure the length of your spring without
any hanging masses.
3. Hang a mass of 100g on the spring
4. Measure the new length of the spring
5. Calculate the extension of the spring
6. Repeat steps 3-5 for increasing the mass
in increments of 100g
7. Take note of your results in the table.

## 1.24 describe elastic behaviour as the ability of a material to recover its original shape after the forces causing the deformation have been removed

Elastic behaviour is the ability of a material to recover original shape after the force is removed. in a spring this occurs when the force is lower than the elastic limit. loading and unloading force extension curves can be different as long as it returns to its original shape.

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Section 1: Principles of chemistry

a) States of matter

b) Atoms

c) Atomic structure

d) Relative formula masses and molar volumes of gases

e) Chemical formulae and chemical equations

f) Ionic compounds

g) Covalent substances

h) Metallic crystals

i) Electrolysis

Section 2: Chemistry of the elements

a) The Periodic Table

b) Group 1 elements: lithium, sodium and potassium

c) Group 7 elements: chlorine, bromine and iodine

d) Oxygen and oxides

e) Hydrogen and water

f) Reactivity series

g) Tests for ions and gases

Section 3: Organic chemistry

a) Introduction

b) Alkanes

c) Alkenes

d) Ethanol

Section 4: Physical chemistry

a) Acids, alkalis and salts

b) Energetics

c) Rates of reaction

d) Equilibria

Section 5: Chemistry in industry

a) Extraction and uses of metals

b) Crude oil

c) Synthetic polymers

d) The industrial manufacture of chemicals