4Q 5week Test Notes
Concept 1: Gravity
How do I increase the force of gravity on an object?
Change:__Mass of object___________________________________________
Change: ___Mass of planet________________________________________
Change:____Distance to center of mass________________________________
Concept 2: Weight and Mass
What is mass?__Amount of matter in an object_____________________________
What is weight?___Force of gravity___________________________________
Concept 3: Inverse square law
What is the inverse square law?______Force diminishes or increases with the square of the
ratio of the distance_____________________________________________
Name some examples of things it applies to:______Gravity__________________
__Electric charge_____________________________________________________
__Sound_______________________________________________________
__Water waves___________________________________________
Problems:
1) What is the mass of a 10kg object on Jupiter (where gravity is 3x stronger than the
Earth’s?)_____________10kg______________________________________________
2) What is the weight of a 10 pound object on the moon (where the force of gravity is 1/6
that of the Earth?)______10/6 = 1.67pounds___________________________________
__________________________________________________________________________
3) If I double the mass of an object, how does that affect the force of gravity acting on the
object?___________________Doubles________________________________
4) If I double the mass of the Earth, how does that affect the weight of my 10 pound cat?
________Doubles it to 20 pounds___________________________________
5) If I double the distance between my cat and the Earth, how does that affect his weight?
_______Cuts it by 4 to 2.5 pounds________________________________
What is my cat’s new weight?___2.5 pounds____________________________
6) If I triple the distance between my cat and the Earth, how does that affect his weight?
_______Reduces by 9_________________________________________
What is my cat’s new weight?________10/9 = 1.11 pounds_______________
7) What is my cat’s
name?___________MWANE____________________________________
8) What is the mass of my 10 pound cat? (Hint: The mass of a 1 pound object is 1/(2.2kg)
on the Earth’s surface.______4.7 kg________________________________________
9) Why do I need to tell you where my cat is before you can answer the question above?
Concept 4: What is a wave?_____A periodic motion______________________
___________________________________________________________________________
What is the wavelength of a wave?____Length from peak to
peak_____________________________
What is the frequency of a wave?___Number of waves per second_____________________
What is the period of a wave?______Time for one wave___________________
What is the amplitude of a wave?____Height of the wave (from the equilibrium)___
What is a node?____Point where the wave is not moving (min amplitude)_____
What is an antinode?_____Point of max amplitude______________________________
What is refraction?__Bending of light moving from one medium to another________
What are some examples of refraction?___Stick in water, light ray passing from water to air_
What is reflection?__Wave bouncing off a surface____________________
What are some examples of relection?___Mirror____________________
What is the rule for reflection?____Angle of incidence = angle of reflection_____
What is resonance?__Response excited in one material by a wave coming from
another___________
Provide an example of resonance:_Tuning forks causing other tuning forks to vibrate_____
What is the Doppler effect?_Change in apparent frequency due to relative motion ___
Explain when you might hear it:__Train at intersection__________________
Wave problems
Two pictures of a wave are provided below, showing different charactersitcis. For the wave
below, what are the values of
Amplitude?___1m_________________
Period?_________2 sec______________
Frequency?______0.5 sec______________
Wavelength?_____2m_____________________
Speed?______v = f lambda = (0.5)(2) = 1m/sec_________________________
A Wave
1.5
M
1
e 0.5
t
0
e
-0.5 0
r
-1
s
-1.5
0.5
1
1.5
2
2.5
2
2.5
Time in seconds
A Wave
1.5
M
1
e 0.5
t
0
e -0.5 0
r
-1
s -1.5
0.5
1
1.5
Distance in meters
Practice with the general wave equation: v= fλ
1. What is the v if λ= 8 m and ƒ = 20 Hz? 160 m/s
2. What is the λif v = 50 m/s and ƒ = 25 Hz? 2m
3. What is the ƒ if v = 50 m/s and λ= 10 m?
5 cycles/s
4. What is the v if λ= 1 m and ƒ = 345 Hz?
345 m/s
5. What is the λ if v = 100 m/s and ƒ = 3 Hz? 33.3m
6. What is the ƒ if v = 120 m/s and λ= 3 m? 40 cycles/sec
7. What is the v if λ= 3 m and ƒ = 10 Hz?
30 m/s
8. What is the λ if v = 345 m/s and ƒ = 790 Hz? 0.44 m
9. What is the ƒ if v = 345 m/s and λ= .25 m? 1380 cycles/sec