### Tutorial 1

**1. A rock of mass 2000kg is placed 340m from another rock of mass 5400kg. **
**1.1.** State Newton's Law of Universal Gravitation as an equation.

1.1.

**1.2.** Calculate the magnitude of the gravitational force of attraction between the rocks.

1.2.

**1.3.** What is the nature of the force?

1.3. attractive

Gravitational forces are always attractive.

**1.4.** What would happen to the size of these forces if the objects were moved closer?

1.4.

The sizes would increase.

inverse proportion

**2. The gravitational force of attraction between two objects X and Y, **

is 2 x 10^{-4}N. The mass X is 2300kg and that of Y is 9890kg.

**2.1.** Determine the distance between their centres.

2.1.

**2.2.** What would happen to the magnitude of the forces if the distance was increased?

2.2. The forces would decrease.

inverse proportion

**3. The gravitational force of attraction between two masses P and T, **

is 5 x 10^{-2} N.
If the mass of P is 70kg and the distance between them is 200cm, calculate the mass of T.

3.

Convert the 200cm to 2m.

(divide by 100)

**4. What is the name for the force with which the Earth attracts an object?**

**A.** gravity

**B.** weight

**C.** mass

**D.** inertia

4.

B. weight

Weight is a force.

**5. Halley's comet, of approximate mass 1 x 10**^{15} kg was 1,3 x 10^{8} km from the Earth's center,
at it's closest approach during it's last sighting in 1986.

**5.1.** Name the force via which the Earth and the comet interact.

5.1. gravitational force

**5.2.** Is the magnitude of the force experienced by the comet **the same, greater than or less than**
the force experienced by the Earth? Explain, using a specific law of physics.

5.2. the same

This is because of Newton's Third Law of Action and Reaction.

**5.3.** Does the acceleration of the comet **increase, decrease of remain the same** as it moves closer to the Earth. Explain.

5.3. increase

The force increases as it gets closer to the Earth. From Newton's Second Law, the acceleration must increase.

**5.4.** Determine the distance between the Earth and Halley's Comet in meters.

5.4.

To convert **km** to **m** you must multiply by **1000** or **10**^{3}.
**5.5.** If the mass of the Earth is 5,98 x 10^{24} kg, calculate the magnitude of the force exerted by the Earth on Halley's comet at it's point of closest approach.

5.4.