1. Forces
Physics on the Road
Lesson 10

2. Isaac Newton’s Law
We are learning to….
 understand that the
acceleration of something
depends upon it’s mass
and the resultant forces
acting on it.
 recall and use the
formula
Force = mass x acceleration
(F=ma)
 Investigate the effects of
an unbalanced force
using equations of
motion.

3. Linking force and motion
Philosophers and
scientists have been
linking force to motion
since 300 B.C.
Not always well.
Forces keep
things moving
Aristotle 325 BC
Forces cause
motion but are
not needed to
keep them
moving
Galileo 1630
Close
but no
cigar
Newton 1675

4. Newton’s Laws
 First Law
If there is no resultant force an
object will remain at rest or if
moving continue moving at a
constant speed.
 Second Law
If there is a resultant force an
acceleration proportional to
the force will occur.
Inertia
Reluctance to change
speed.
Depends upon mass.
Force = mass x acceleration
(N) (kg) (m/s2)
m x a
F

6. Calculation Questions
F
U
N
C
A
U
Q1. What force is
needed to give the
800 kg drag car an
acceleration of 5
m/s2?
Q2. A rocket has a mass of
5000 kg. It’s engines provides
a force of 200 000 N. What is
the rocket’s
acceleration?

7. Wacky Race
Boeing 747
Mass = 200 000 kg
Engine Force = 500 000 N
Porsche 911
Mass = 1500 kg
Engine Force = 9000 N
Honda CBR
Mass = 200 kg
Engine Force = 1600 N
m x a
F
a = F / m
= 500000 / 200000
= 2.5 m/s2
a = F / m
= 9000 / 1500
= 6 m/s2
a = F / m
= 1600 / 200
= 8 m/s2

8. Forces cause acceleration
What can we
vary?
What will that
vary?
How should we
measure this?

9. Experiment design
 Can we measure the acceleration?
 Are there other measurements we can
make to calculate the acceleration?
 Design your experiment and data table
carefully.