10.2 Forces
Name: ____________________
What is a force? a push or pull
What is gravity? the force of attraction between all objects
Is there gravity between a pencil and a pen? Explain. Yes, there is, because gravity is between ALL
objects. It’s just so weak you don’t notice it.
What is an applied force? a force when the objects come in contact
Give 3 examples of applied forces:
1. your foot pushing down on a bike pedal
2. a raindrop hitting a window
3. a hockey stick hitting a puck
Forces Have Magnitude and Direction
Every force has a strength and a direction.
In figure 6, which force is stronger? (circle answer):
(a)
or
(b)
How do you know? the arrow is thicker (the thicker the arrow, the stronger the force)
Distinguishing between Mass and Weight
What is mass? the quantity of matter in an object
What units are used for mass? grams, kilograms, etc. (g, kg, etc.)
Where have you seen mass used before?
1. the amount of chicken meat in a package
2. exercise equipment (barbells etc.)
What is weight? a measure of the force of gravity pulling down on an object
What units are used for weight? Newtons (N)
Note: another unit commonly used to measure weight is pounds (lbs)
Where have you seen weight used before?
1. stepping on a scale
2. buying bananas
Why do people use mass and weight as if they are the same thing on the Earth?
because the force of gravity on the Earth’s surface is fairly constant (note: the higher up
you go (altitude), the less the force of gravity)
Explain why a person who weighs 180 lbs would weigh 30 lbs on the moon?
Weight is the force of gravity acting on an object. On the Moon, the gravity is one-sixth
as much as the Earth, so the weight would be one-sixth as much (180 ÷ 6 = 30)
If the person’s mass is 82kg, what would his/her mass be on the moon? 82kg
Why?
Mass is the quantity of matter in an object. Mass remains the same anywhere in the
universe. It doesn’t depend on gravity like weight does.
What would the person’s mass be on Pluto? 82kg
Loads
What is a load? a force acting on a structure
What is a static load? a load that results from gravity
Fill in the following table:
2 types of static load
definition of each type of static load
one example of each
1.
dead load
the weight of the structure itself
the weight of a bridge
2.
live load
the weight of the objects that a
the weight of the cars on a
structure supports
bridge
What is a dynamic load? a load caused by forces other than gravity
Give an example from the text: moving water rushing against a bridge
Give an example that’s not in the text: a person jumping on a diving board
Check Your Learning
For extra practice, do questions #1-4 on a separate sheet of paper. Remember to word your answers in a way so
that someone could read your answers and be able to know exactly what the question was asking.