1. DO NOW QUESTION
Say you become an astronaut. Will you WEIGH more, less, or the same on the moon?
Less
Why?
Because the moon has less gravity than Earth.

2. Notes: Mass Vs. Weight OBJECTIVE: Students will be able to (SWBAT)…
Distinguish between mass and weight.

3. Units of force
The pound is a unit of force commonly used in the United States.
For smaller amounts, pounds are divided into ounces (oz.).
There are 16 ounces in 1 pound.

4. Newtons
Although we use pounds all the time in our everyday life, scientists prefer to measure forces in newtons.
The newton (N) is a metric unit of force.

5. Unit conversions
The newton (N) is a smaller unit of force than the pound (lb).
If one pound of force equals newtons, then a 100 lb person weighs newtons.

6. Gravity and Weight
The force of gravity on an object is called weight (Fw or Fg).
At Earth’s surface, gravity exerts a force of 9.8 N on every kilogram of mass.

7. Weight vs. mass Weight and mass are not the same.
Mass is a fundamental property of matter measured in kilograms (kg).
Weight is a force measured in newtons (N).
Weight depends on mass and gravity.

8. Weight depends on mass and gravity
A 10-kilogram rock has the same mass no matter where it is in the universe. On Earth, the10 kg rock weighs 98 N. On the moon, the same rock only weighs 16 N.

9. Weight and mass
Legend says that about 1587, Galileo dropped two balls from the Leaning Tower of Pisa to see which would fall faster. Suppose the balls had masses of 1.0 kg and 10 kg.
Use the equation for weight to calculate the force of gravity on each ball.
Use your answers from part a and Newton’s second law to calculate each ball’s acceleration.

10. Given: … one ball’s mass = 1.0 kg.
Weight and mass
Looking for: … the force due to gravity (Fw) and the acceleration for each ball
Given: … one ball’s mass = 1.0 kg.
Relationships: Use: Fw = mg and a = F ÷ m
Solution: For the 1.0 kg ball:
a) Fw = (1.0 kg)(9.8 m/s2) = 9.8 N
b) a = (9.8 N) ÷ (1.0 kg) = 9.8 m/s2

11. Given: … other ball’s mass = 10 kg.
Weight and mass
Looking for: … the force due to gravity (Fw) and the acceleration for each ball
Given: … other ball’s mass = 10 kg.
Relationships: Use: Fw = mg and a = F ÷ m
Solution: For the 1.0 kg ball:
a) Fw = (10 kg)(9.8 m/s2) = 98 N
b) a = (98 N) ÷ (10 kg) = 9.8 m/s2

12. Gravity is the same force on both, but the weight is different.
Weight and mass
Both balls have the same acceleration, so they would fall at the same time.
Gravity is the same force on both, but the weight is different.
What could make them fall different? Think about a feather.

13. Review: Distinguish between mass and weight.
Mass is the ________ on Earth & the Moon, but weight is _________.
_____________ measure matter.
_____________ is dependent on mass and gravity.
Gravity is equal to ______ m/s2.
If mass in 10kg, what is the weight on Earth? ___________
If the weight on Earth in 500N, what is the mass? _________

14. 5:40 EXTRA VIDEO