Warm Up: Gravity Inquiry Use the cards in the envelope to develop a relationship between: Mass and Force of Gravity Distance and Force of Gravity Mass, Distance, and Force (Create an Equation)
Warm Up: Today we are doing a THINK, PAIR, SHARE. The THINK is your warm up and is to be done silently and on your own. If you haven’t already, grab an envelope, take out the cards, arrange the cards into an order that makes sense to you and on a sheet of lined paper write down what you notice in the “Initial Thoughts” column You have 8 minutes.
PAIR Share what you noticed with your partner. Come up with reasoning for your noticings. Put these in the “Final Thoughts” Column
Class Share Let’s chart our noticings. Add any new information to your “Final Thoughts” column
Gravity Equation why, then, student A and student B are not being pulled towards one another? What does G do to our values of our forces?
Universal Gravitational Constant The magnitude of the force between two masses of 1 kilogram each, 1 meter apart was calculated to be 0.0000000000667 Newton's by an English physicist, Henry Cavendish. But how does that make sense? .0000000000667
G – The Universal Gravitational Constant G = 6.67x10-11 Nm2/kg2 The value of G tells us that the force of gravity is a very weak force. It is the weakest of the presently known four fundamental forces. (The other three are the electromagnetic force and two kinds of nuclear forces.) The force of attraction between you and a classmate is too weak to notice (but it’s there!).
r
Practice Problem M1 = 70 kg M2 = 80 kg r = 10 m G = 6.67x10-11 FG= ?
Inverse square law An apple weighs 1 N at Earth’s surface. It weighs only 0.25 N when located twice as far from Earth’s center because the pull of gravity is only 1/4 as strong. When it is 3 times as far, it weighs only 1/9 as much, or 0.11 N
Take a look at the numbers Mass 1 Mass 2 Distance Between Masses Force of Gravity 1 1/1 = 1 2 1/4 = 0.25 3 1/9 = 0.11 4 1/16 = 0.0625 5 1/25= 0.04 6 1/36= 0.028
How massive is the Earth!? Remember the old spring scale… The force applied to the spring scale by the Earth, when we hang a 1 kg mass on it, is 10 N. If the radius of the Earth is 6,371,000 m, what is the mass of the Earth? 6.085x1024kg
Nothing but a G thing. Now that we know that the mass of the Earth is 6.09 x1024 kg, if Gloria has a mass of 4.86 kg and the distance between her and the center of the Earth is 6,371,000 m. What is the force of gravity between her and the Earth? If Gloria were on the moon, which has a radius of 1,738,000 m, what is the force of gravity between her and the moon? The moon has a mass of 7.35x1022 kg
The average distance between you and me is 5 meters. If my mass is 79 The average distance between you and me is 5 meters. If my mass is 79.5 kg and yours can be found by taking your weight and dividing by2.2, what is the force of gravity between us?
Exit Ticket On the BACK of your worksheet… Summarize what you learned today. Try this problem: M1 = 6x1024 kg M2 = 7.35x1022 kg r = 363,104,000 m G = 6.67x10-11 FG= ?
Summary The force due to gravity is very weak. It depends directly on the masses of the two objects in question. There is an inverse square relationship between the distance between the objects and the force of gravity. There is a gravitational force between ALL objects. May the force be with you!