Presentation on theme: "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."— Presentation transcript:
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
Newtons Law of Universal Gravitation
Sir Isaac Newton ( )
R earth 60R earth
Newtons Law of Gravity M1M1 M2M2 r Constant of proportionality
Cavendish, Henry ( ) Measured G in 1798 G = 6.67 x Nm 2 /kg 2
What is the force between Kiwi and a book? 4 kg F = (6.67 x ) (3)(4)2 F = 2 x N 2 m 3 Kg
What is the force between Kiwi and a book? F = (6.67 x ) (3)(4)2 F = 2 x N F cat, book F book, cat or ?? 1,21,2 4 kg 3 Kg
M earth = 5.98 x kg r = 6.38 x 10 6 m What is the force between the Earth and a book? W earth,book = M book (9.8 N/kg) W earth,book = (6.67 x Nm 2 ) (5.98 x kg) M book (6.38 x 10 6 m) 2 kg 2
But you ask why is g independent of mass? zF = m 1 g = Gm 1 m earth /r 2 zNote that the m 1 s cancel on both sides and: zg = Gm earth /r 2
Storey Musgrave ( 6 SST missions and Hubble Repair) m = 80 kg
Whats his mass?
Whats his weight? 648 N !
Apollo 17 Earth as seen from the Moon
What is the correct orbit of the space shuttle?
At the surface of the Earth: r earth = 4000 miles W earth,Story = M Story (9.8 N/kg) = (80 kg) (9.8 N/kg) = 784 N
400 miles above the surface : r earth = 4000 miles W earth,Story = M Story (8.1 N/kg) = (80 kg) (8.1 N/kg) = 648 N
W EP N SP person Which force does the scale read? N FS W ES N PS 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 W EP N SP v = constant a = 0 Apparent Weight True Weight
Elevator W EP N SP a is upward a Apparent Weight True Weight
Elevator W EP N SP 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 W EP N SP How large should the normal force be? a =9.8 m/s/s down g
Elevator W EP a =9.8 m/s/s down How large should the normal force be? g Weightless?? Apparently