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5.2
USING NEWTON'S LAW
Mass and Weight
An object's weight is the (1) force acting on the object. The unit used to express measurements of weight is the (2).
Newton's (3) law can be used to find the weight of an object. The acceleration caused by gravity is equal to (4), and
is represented by the symbol (5). The equation used for calculating weight is (6). According to the equation, an
object's weight is proportional to its (7). An object's weight may vary from one location to another, because (8) may
change from one place to another. However, the object's (9) does not change.
Two Kinds of Mass
One way to determine mass is to measure the amount of (10) needed to accelerate the object. This is called (11)
mass. The other way to determine mass is to use a balance to compare the effects of (12) force on two objects.
This is called (13) mass. In experiments, these two determinations of mass have been shown to be (14).
Friction
If you push on an object and slide it across a surface, the force of friction will (15) the motion. Friction acts in a
direction that is (16) to the surface on which the object slides, and (17) to the direction in which the object slides.
(18) friction opposes the start of an object's motion, and (19) friction opposes continuing the motion when the object
is already in motion. Of these two forces, (20) friction is greater. The amount of friction can be calculated using the
equation (21). The constant in the equation is called the (22).
The Net Force Causes Acceleration
If more than one force acts on an object, the amount of acceleration can be calculated using Newton's (23) law.
However, before the equation in Newton's law is used, the net force, which is the (24) of the forces, must be found.
The positive and negative signs on the forces are important because they indicate the (25) of the forces.
The Fall of Bodies in the Air
Without any air, all objects fall with the same (26). When air is present, a friction-like force, called the (27), acts on
the object. This force depends on the (28) and (29) of the object, the (30) of the air, and the (31) of motion. When
this force is equal to the force of gravity, the net force on the object is (32), and the object has reached its (33)
velocity.
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