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)
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 10-11 Nm2/kg2
What is the force between Kiwi and a book? F = (6.67 x 10-11) (3)(4) 22 F = 2 x 10-10 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 10-10 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