2. FIRSTUP
CONSULTANTS 2
C. Mass and Weight
The force of the object due to gravity is called
weight. Therefore, using Newton’s second law, the
magnitude of weight w of an object is defined as:
w = mg
where m is the mass of the object and g is the
acceleration due to the gravity.
g = 9.8 m/s2
3. FIRSTUP
CONSULTANTS
Since weight is a force, the SI unit of weight is a newton. For example, a 1-
kilogram mangoes has a weight of 1.0 kg x 9.8 m/s2 = 9.8 N.
Mass and weight are proportional to each other, they are not the same. Mass is the
measure of the amount of matter in an object and in constant. Weight on the other
hand, is the force of gravity on an object and it varies from one planet to another.
4. FIRSTUP
CONSULTANTS 4
D. Friction
Friction is a force that opposes motion between two surfaces. It always acts
opposite the direction of motion or an impending motion. The amount of friction
present between surfaces depends on two surfaces involved. Generally, the rougher the
surfaces are, the greater the friction will be. Aside from the roughness of the surface
involved, the amount of friction also depends on the force pushing the surfaces
together.
6. FIRSTUP
CONSULTANTS 6
E. Uniform Circular Motion
Uniform circular motion is the motion of an object
moving at a constant speed in a circular path. As the object
moves in a circle, its direction changes constantly. The direction
change is directed towards the circular path. Because of this
change in direction, you know that the object is accelerating
(even if it is moving at a constant speed).
The direction of the acceleration, which is inward, is the same as
the direction of the net force. This inward net force is called
centripetal force.
