Gravity - mutual force of attraction between any two objects in the universe

Fill In The Blank Notes

Warm-Up

Do Now warm-up prompt

Explain why the bottom stream is faster than the top.

Leaky Bottle and Water Pressure

Show Me The Physics YouTube Channel

C) Universal Law of Gravity

Gravity by John Mayer II

Newton's Cannon diagram
Image found on Wikipedia
Newton and the apple tree

Moon Has An Unbalanced Force On It!

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F = Gm1m2 r2

G = Gravitational constant = 6.67 × 10-11 Nm2/kg2

Physics reference table constants
(Reference Table p. 1)

m1, m2  — two masses

Two masses m1 and m2 separated by distance r

r — distance between center of masses

Giancoli p. 131 – #28 Giancoli practice problem 28

F = Gm1m2 r2

Fg proportional to product of two masses

Fg m1 m2
100 Nxy
200 N2xy
600 N2x3y
400 Nx4y
150 N1/2x3y
Gravitational force and mass reference diagram

F = Gm1m2 r2

Fg inversely proportional to the square of distance between the object's center of mass

Inverse square law diagram

Gravity, Newton, and Hooke - The Bitter Rivalry

Fg r
x1/4x2
x1/9x3
x1/16x4
x9x1/3
x16x1/4
Satellites A and B diagram

Ex) If the gravitational force on satellite A is 160,000 N, what is the gravitational force on satellite B?

↓

F = 40,000 N

(twice distance, 1/4 the force)

Fluids in Micro-Gravity

Ranking Task

Rank the gravitational forces from greatest to smallest.

Ranking task diagram of gravitational forces

Enrichment

How do we measure very tiny gravitational forces?

Physics for the 21st Century

Determining G, Cavendish

Video

Penn State Physics

Dark Matter

Newton's law of gravitation, F = G m1 m2 over r squared, with Earth and Moon pulling on each other, beside Einstein's curved space-time grid around the Sun NYSSLS Reading Passage icon

NYSSLS Reading Passage · Dynamics

The Law That Can't Explain Itself: Gravity and the Biggest Myth in Science

Open Reading Passage → Regents Practice Version →

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. What is gravity?

2. In F = Gm₁m₂/r², what does r represent?

3. If the distance between two objects is tripled, the gravitational force between them becomes…

4. Two masses attract with a force of 100 N. If one mass is doubled and the other is tripled (same distance), what is the new force?

5. The gravitational force on satellite A is 160,000 N. Identical satellite B orbits at twice the distance from Earth's center. What force acts on B?

NYSSLS Regents Practice · Dynamics · Gravitational Interactions

Floating on the Space Station

The International Space Station (ISS) orbits about 400 km above Earth’s surface, or about 6.8 × 106 m from Earth’s center. Earth’s radius is about 6.4 × 106 m. Astronauts aboard the ISS appear to float.

Which statement best explains why astronauts float aboard the ISS?

▶ Want a challenge? Open 6 more Regents-style questions  (harder · mixed formats)

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Multiple choice

C1. How does the gravitational force Earth exerts on the Moon compare with the force the Moon exerts on Earth?

Substitute values

C2. Using g = 9.8 m/s² at Earth’s surface, substitute numerical values into a mathematical representation that can be used to determine the gravitational field strength at the ISS. Then calculate it.

gISS = gsurface(REarthrISS)2 = ( m/s2)( × 106 m × 106 m)2 = m/s2
Determine the value

C3. Gravity at the ISS is about 8.7 m/s². Determine the magnitude of the gravitational force on a 70.-kg astronaut aboard the ISS.

Fg = N
Support or Refute · Justify

C4. A student makes the following claim.

Claim: If the ISS orbited twice as far from Earth’s center, the gravitational force on it would be half as large.

Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.

Multiple choice

C5. Which graph best represents the gravitational force between two objects versus the distance between their centers?

Constructed response

C6. Gravity at the ISS is about 89% as strong as at Earth’s surface, yet astronauts float. Identify the evidence that gravity still acts on the ISS, and explain why astronauts nevertheless feel weightless.