2. Force
A push or a pull exerted by one object on
another body.
The effect of force is to tend to change the
state of motion of the body on which it acts.
It is a vector quantity
Represented by SI unit “N”
3. 2 General Types of Forces
Non-fundamental Forces
Ex. ordinary push and pull forces and friction
Fundamental Forces
Ex. Gravitational Force, Magnetic Force, Strong
Nuclear Force, and Weak Nuclear Force
4. The Fundamental Forces
Gravitational Force
The force of attraction
between objects by virtue
of their masses and is
responsible for weights of
the bodies on Earth as
well as the motion of the
planets
8. CONTACT AND NON-CONTACT
FORCES
Contact forces- forces that result from direct
physical contact between two objects.
Non-contact forces- forces that do not
involve direct physical contact
9. Mass versus Weight
Mass- the quantity of matter a body contains
A vector quantity
SI unit “kg”
Weight- the force on a body due to gravity
A scalar quantity
SI unit “N” for Newton
Mass and Weight Relationship
W=mg
10. Sample Problem
Lynne has a mass of 100.0 kg on Earth. What is her weight on Earth? What
is her weight on the moon? What is her weight on the moon where the
acceleration due to gravity is 1/6 that of the Earth?
Solutions:
Given: m= 100 kg W=mg
W=(100kg)(9.8m/s2)
W= 980 N
On the moon, her mass will not change but her weight will change
W=(100kg)(9.8m/s2)
W= 163 N
6
11. Practice exercise
Andee has a mass of 68.5 kg on Earth. What is
his weight of Earth? What should his mass be in
order to have the same weight at the surface of
the moon?