Various Forces
&
Mass
Force
Push or pull
•Measured in Newtons (N) in the SI system
•Vector quantity
• 1 N is approximately equal to one-fourth of a pound
(the weight of an apple)
• 1 Newton is the amount of force required to accelerate
a 1 kg mass at 1 m/s2
Four Fundamental forces:
1) Gravitational (Weakest force)
2) Electromagnetic (2nd strongest force)
3) Strong Force (Strongest force)
4) Weak Force (2nd weakest force)
Gravitational Force

The attractive force between masses
Electromagnetic


The inherent force between stationary
or moving protons and electrons on
other charges
This force is responsible for giving
matter its properties and strength.
Strong Force

The force responsible for binding the
protons and neutrons of an atom
together.
Weak Force

The force responsible for radioactive
decay.
Weight





The gravitational force exerted by a
celestial body on a mass.
Varies depending on the acceleration due
to gravity (gravitational field).
Decreases as the height above the
celestial body significantly increases.
Vector quantity.
Measured in Newtons
 W=mg

(use the negative sign when other vectors are involved in the
problem)
Mass
Mass- a measure of the amount of matter that makes up an object
1 kg =2.2 lbs
Inertia – the resistance of a mass to change its state of motion
 Inertia – is an indirect measure of mass (the more mass an object
has the greater the inertia)

Mass stays the same regardless of weight or the acceleration due to
gravity
Inertial Mass- the mass calculated from the ratio of the net force to
acceleration
(Fnet/a)
 Gravitational Mass - the mass calculated from the ratio of the
weight of an object to the acceleration due to gravity.
(W/g)
The mass calculated is equivalent by both methods of calculations.
Normal Force



The amount of perpendicular force between
two surfaces in contact
The normal force is directed away from the
surfaces in contact.
Weight is equal to the amount of
normal force on a non-accelerating
horizontal surface without additional forces
N
N