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P10.1
Student literacy sheet
Name ......................................................................
Class ..................
Date ......................
Newton’s three laws of motion
Specification references:
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P6.2.1 Newton’s First Law
P6.2.2 Newton’s Second Law
P6.2.3 Newton’s Third Law
Aims
This is an activity that has been designed to help you improve your literacy skills.
In this activity you will learn more about Newton’s three laws of motion and how
they can be used in conjunction with one another to describe the behaviour of
bodies that are stationary, moving at a constant speed, or accelerating. You will
practise answering questions that involve some of the key command words and
scientific terms that you will encounter in the topic of forces and motion.
Learning outcomes
After completing this worksheet, you should be able to:
 state Newton’s three laws of motion
 define terms such as inertia, action, and reaction
 describe the relationship between force, mass, and acceleration
 explain when each of Newton’s three laws is being applied to a problem
 apply Newton’s laws to a problem.
Setting the scene
Isaac Newton’s First Law describes why bodies remain at rest or move at a
constant speed. Newton’s Second Law of motion explains the relationship
between force, mass, and acceleration for bodies in motion, and Newton’s Third
Law describes how forces act in pairs. There are a number of misconceptions that
you may have about Newton’s laws of motion which will be addressed in this
worksheet.
Task
Read the text about Newton’s three laws of motion and then answer the questions
that follow.
Newton’s First Law:
An object at rest tends to stay at rest and an object in motion tends to stay in
motion with the same speed and in the same direction unless acted upon by
an unbalanced external force.
Inertia is a property of matter that resists a change in motion of a body. If a mass
is not moving, it will stay that way until an unbalanced external force acts on it; if a
mass is moving at a constant speed it will stay moving at that speed and in the
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
1
P10.1
Student literacy sheet
Name ......................................................................
Class ..................
Date ......................
same direction until an unbalanced external force changes acts on it to change its
speed or direction. For example, unbalanced forces include friction to slow the
object down, or a driving force could cause the object to accelerate. Inertia
depends on the mass of the body – the greater the mass, the more inertia it will
possess.
As an example of Newton’s First Law, consider a car accelerating from rest at
traffic lights. As the car accelerates from a stationary start, your body tends to
push back into the seat due to its inertia. Your body is trying to remain at rest and
resist the change in motion of the car. Also, when the car’s brakes are applied
from a high speed, your body is thrown forward due to its inertia in motion – it
wants to continue moving and opposes the change that is trying to slow it down.
Newton’s Second Law:
A resultant, or net, external force F acting on a body of mass m will accelerate
that body with acceleration a (in the direction of F ) according to the equation:
Force F (N)  mass m (kg) × acceleration a (m/s2)
Before Newton stated his Second Law, people thought that force was proportional
to velocity, which would give the equation F  mv. However, a body will actually
move at a constant speed if the forces on it are balanced. The product mv is not
equal to force, but to momentum. Momentum is related to force by the equation:
force F (N) 
change in momentum mv (kg m/s)
change in time t (s)
Newton’s Third Law:
For every action, there is an equal and opposite reaction.
In order to walk across the floor, you must push back on the floor with your foot;
then, according to Newton’s Third Law, the floor pushes forward on your foot,
which propels you forward. This, of course, requires friction to work. The recoil of
a gun during firing is another example of Newton’s Third Law. As a final example,
if a person attempts to jump from a small boat to a jetty, they may end up landing
in the water if they do not understand Newton’s Third Law. The jumping force of
the human on the boat will tend to push the boat backwards; the equal and
opposite force of the boat on the human will propel that person toward the jetty.
However, since the boat moves backwards, the person may end up falling into the
water between the boat and the jetty! The same problem exists for large boats;
however the larger boat has a larger inertia, and so it is less likely the person will
fall into the water.
Newton’s Third Law requires the two forces to be of the same type, acting in
opposite directions, and acting on different objects.
Questions
1
Newton’s first law refers to ‘inertia’.
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
2
P10.1
Student literacy sheet
Name ......................................................................
2
3
Class ..................
a
Define ‘inertia’.
b
State what quantity determines the magnitude of a body’s inertia.
c
Describe two examples where inertia is observed in nature.
Date ......................
What are the conditions that are necessary for a body to be:
a stationary?
b
moving at a constant speed?
c
moving with a constant acceleration?
Explain what the term ‘resultant force’ means.
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
3
P10.1
Student literacy sheet
Name ......................................................................
Class ..................
Date ......................
4
Suggest why, before Newton formulated his three laws of motion, people
believed that F  mv and not F  ma.
5
Newton’s Third Law requires the two forces acting to be of the same type,
acting on different bodies and acting in different directions. Give an
explanation of one example from the text, in relation to Newton’s Third Law.
6
A book placed on a table is being acted on by the force of gravity. A student says
that Newton’s Third Law states that this force will be equal and opposite to the
reaction force of the table pushing up on the book. The student is incorrect.
Explain why the student is incorrect and state what she should have said.
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
4