# 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.

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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 ( )

Rearth 60Rearth

Newton’s Law of Gravity
Constant of proportionality M1 M2 r

Cavendish, Henry (1731-1810) Measured G in 1798
G = 6.67 x Nm2/kg2

What is the force between Kiwi and a book?
F = (6.67 x 10-11) (3)(4) 22 F = 2 x N 2 m 4 kg 3 Kg

What is the force between Kiwi and a book?
1,2 F = (6.67 x 10-11) (3)(4) 22 F = 2 x N or ?? F cat, book F book, cat 4 kg 3 Kg

What is the force between the Earth and a book?
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)2 kg2 r = 6.38 x 106 m Mearth = 5.98 x 1024 kg

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:
Wearth,Story = MStory (9.8 N/kg) = (80 kg) (9.8 N/kg) = 784 N rearth = 4000 miles

400 miles above the surface :
Wearth,Story = MStory (8.1 N/kg) = (80 kg) (8.1 N/kg) = 648 N rearth = 4000 miles

Which force does the scale read?
NFS WES NPS scale WEP NSP person 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 v = constant a = 0 NSP Apparent Weight True Weight WEP

Elevator NSP a is upward a Apparent Weight True Weight WEP

Elevator a is downward a Apparent Weight True Weight NSP WEP

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 g How large should the normal force be? a =9.8 m/s/s down NSP
WEP

Elevator Apparently Weightless?? g
How large should the normal force be? a =9.8 m/s/s down Apparently g Weightless?? WEP

KC 135 INTERIOR

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