Physics 2

1
Interaction between objects
GCSE Additional Science
Chapter 15
Physics 2
2
Forces working in Pairs
Force A that you exert on the trolley.
Force B exerted by the trolley (on you) it is
equal and opposite to force A.
Force A
Force B
Constant speed
GCSE Additional Science
Chapter 15
3
Work Done
Distance Force moved (m)
As an object is moved, you do WORK and you have
to use energy. To calculate the work done, you
must use
GCSE Additional Science
Chapter 15
Work (J) Force (N) x Distance Force moved (m)
4
Example Questions
25J
20J
4m
50N
2MJ

1. Sion pushes a block 5m across a table with a
   force of 5N. He tires and stops. How much work
   did Sion do?
2. Anna lifts her school bag 2m up in the air with a
   force of 10N. How many times did she do it?
3. Mathew does 200J worth of work whilst pushing a
   box with the force of 50N. What distance did he
   move the box?
4. Cai lifts his cat 1.5m into the air. If he had
   done 75J worth of work, how much force did he
   use?
5. Carl drives a car over 1000m. If the engine
   exerts a force of 2000N, how much work is done by
   the car?

GCSE Additional Science
Chapter 15
ANSWERS
5
Kinetic Energy
Higher
Every moving body has Kinetic Energy.
It is possible to calculate a moving bodys
kinetic energy by using
Kinetic Energy mass (kg) x speed squared
(m/s)2 2
Kinetic Energy m x v2 2
GCSE Additional Science
Chapter 15
For a diver weighing 70kg travelling at
54m/s Kinetic Energy ½ 70 542
102,060J 102kJ

6
Exemplar Questions
450kJ
4kJ
5m/s
75kg

1. Megan drives her car at a speed of 30m/s. If the
   total mass is 1000kg what is her kinetic energy?
2. Sioneds speed on her bike is 10m/s. The total
   mass of Sioned and her bike is 80kg, so what is
   her kinetic energy?
3. Dan runs with a kinetic energy of 750J. His mass
   is 60kg whats his speed?
4. Geraint walks to school. His kinetic energy is
   150J and his speed is 2m/s, so what is his mass?

GCSE Additional Science
Chapter 15
ANSWERS
7
Potential Energy
HIGHER
Potential energy is the energy that every object
has due to its position.
It is possible to calculate an objects potential
energy by using
Potential Energy mass x gravitational
strength x height (J)
(kg) (m/s2)
(m)
Potential Energy mgh
GCSE Additional Science
Chapter 15
For the book on top of the pile, it has a mass of
0.7kg and its 2m from the floor, so
Potential energy 0.7 10 2 14J

8
Friction

1. What is friction?
2. Give 3 examples where friction can be a problem.
3. Give 3 examples where friction can be useful.
4. What effect does friction have on surfaces?

GCSE Additional Science
Chapter 15
9
Braking Distances for a car

• A cars braking distance is composed of two
  elements
• The thinking distance this is the distance you
  travel whilst reacting.
• Braking distance this is the distance travelled
  whilst braking.

Thinking distance
Braking distance
Total
14m
9m
23m
13m/s (30 m.p.h.)
15m
38m
53m
22m/s (50 m.p.h.)
21m
75m
96m
31m/s (70 m.p.h.)
GCSE Additional Science
Chapter 15
You do not need to learn the above figures for
the exam, but they show how the cars speed
affect its stopping distance. What else affects a
cars stopping distance?
10
A Cars Stopping Distance
High speed
Tiredness
Alcohol
Drugs
Impaired vision
Ice on the road
Wet road surface
Chapter 15
GCSE Additional Science
Worn tyres or brakes
High speed
11
Cars Stopping Distance
Visit the website below to see video clips on the
effects of speed, tiredness, alcohol misuse etc.
on the stopping distance.
http//www.thinkroadsafety.gov.uk/mediacentre/me
diapage.htm
GCSE Additional Science
Chapter 15