Embed Size (px)
DESCRIPTION
Day 59 Physics UCM. LO: SWBAT perform calculate Fc and Ac LO: SWBAT Calculate Fg using NULG AGENDA Do Now – Complete UCM worksheet Notes Worksheet HW22 due Thursday. Newton’s Law of Universal Gravitation. Sir Isaac Newton (1642-1727). 60R earth. R earth. Constant of proportionality. - PowerPoint PPT Presentation
Citation preview
Day 59 Physics UCM
LO: SWBAT perform calculate Fc and AcLO: SWBAT Calculate Fg using NULG
AGENDADo Now – Complete UCM worksheetNotesWorksheetHW22 due Thursday
Newton’s Law of Universal Gravitation
Sir IsaacNewton
(1642-1727)
Rearth
60Rearth
221
r
MMGF
Newton’s Law of Newton’s Law of GravityGravity
M1 M2
r
Constant of proportionality
Cavendish, Henry (1731-1810)
• Measured G in 1798
G = 6.67 x 10-11 Nm2/kg2
What is the force between Kiwi and a book?
4 kg
F = (6.67 x 10-11)(3)(4)
22
F = 2 x 10-10 N
221
r
MMGF
2 m
3 Kg
What is the force between Kiwi and a book?
F = (6.67 x 10-11)(3)(4)
22
F = 2 x 10-10 N
221
r
MMGF
F cat, book F book, cat
or??
1,2
4 kg3 Kg
Mearth = 5.98 x 1024 kg
r = 6.38 x 106 m
What is the force between the Earth and a book? 2
21
r
MMGF
Wearth,book = Mbook (9.8 N/kg)
Wearth,book = (6.67 x 10-11Nm2)(5.98 x 1024 kg) Mbook
(6.38 x 106 m)2kg2
But you ask why is “g” independent of mass?
F = m1g = Gm1mearth/r2
Note that the m1’s cancel on both sides and:
g = Gmearth/r2
Storey Musgrave (6 SST missions and Hubble Repair)
m = 80 kg
What’s his mass?
What’s his weight?
648 N !
Apollo 17
Earth as seen from the Moon
What is the correct orbit of the space shuttle?
What is the correct orbit of the space shuttle?
At the surface of the Earth:
rearth = 4000 miles
Wearth,Story = MStory (9.8 N/kg)
= (80 kg) (9.8 N/kg) = 784 N
400 miles above the surface :
rearth = 4000 miles
Wearth,Story = MStory (8.1 N/kg)
= (80 kg) (8.1 N/kg) = 648 N
WEP
NSP
person
Which force does the scale read?
NFS
WES
NPS
scale
Apparent Weight
True Weight
Apparent weight
• measured as the reading of the scale
• equal to the normal force of the scale on your feet
• equal to weight for a=0
Elevator
WEP
NSP
v = constant
a = 0
Apparent Weight
True Weight
Elevator
WEP
NSP
a is upward
a
Apparent Weight
True Weight
Elevator
WEP
NSP
a is downward
a
Apparent Weight
True Weight
Problem
• You are riding down in an elevator carrying a 20 kg package in your arms. As the elevator gets to your floor, it slows with an acceleration of 2 m/s/s. What is the apparent weight of the package while the elevator is slowing?
Elevator
WEP
NSP
How large should the normal force be?a =9.8 m/s/s down
g
Elevator
WEP
a =9.8 m/s/s down
How large should the normal force be?
g Weightless??Apparently
KC 135
INTERIOR
