This presentation is about Forces and Motion

1. Demonstrating how a body
responds to changes in motion
SCIENCE 8
QUARTER 1

2. How a body responds to changes in motion
Force acting on a body may cause changes in motion.
Push Pull

3. Newton’s First Law of Motion: Law of Inertia
An object at rest will remain at rest; an object in motion will remain in
motion when no external force is acting on it.
Inertia
• Property of an object
that resists change
• Mass dependent Illustration of at
rest / in motion

4. Newton’s First Law of Motion: Law of Inertia
Object at Rest
• An object at rest is acted
upon by a normal force
and gravitational force.
• The box remains at rest
since the two forces
balanced each other and
no other force is acting on
the box.
Example

5. Newton’s First Law of Motion: Law of Inertia
Object in motion
• An object in motion is acted
upon by normal force and
gravitational force.
• The box will remain sliding
since there is no friction
between the box and the
floor and the forces acting on
the box balanced each other.
Example

6. Newton’s First Law of Motion: Law of Inertia
EXAMPLE
External forces
• When the engines are turned
off, a spacecraft in space will
move with constant speed in the
same direction.
• However, when unbalanced
forces such as the force exerted
by the spacecraft’s engine acted
on it; it will change its speed
and direction.
Example