Name: ________________________


                                        Student Number: ______________

Newton's law of motion is: acceleration = force/mass.
The mass of a planet does not change as it orbits the Sun, but the force does. The force acting on a planet is the force of gravity, which is stronger when the planet is closer to the sun and weaker when it is farther away from the Sun. Hence, the acceleration of a planet is smaller when it is farther away from the Sun and larger when it is close to the Sun. Acceleration is the change in velocity. The stronger force of gravity close to the Sun gives the planet a greater acceleration toward the Sun which increases its velocity.

2. Suppose you are in a car and the driver floors the gas peddle. What would you feel?

You would feel pushed backward into the seat with respect to the car. (1 point)

Why do you feel this way? What is really happening?

The car accelerates forward and its speed increases. Your speed remains the same until you are accelerated by the seat back. Hence the car moves forward faster than you move forward, so with respect to the car you feel pushed back into the seat. (4 points)

3. Why is it easy to push a toy sailboat but not a real one?

A toy has less mass than a real sailboat and thus requires less force to obtain the same acceleration, acceleration = Force/mass. (3 points)

4. What property of your motion is described by the statement that you are driving toward Pontiac at 70 mph?

This is a specification of both how fast and the direction you are moving, it therefore describes your velocity. (3 points)

5. When Kepler could not fit Tycho Brahe's observations of the orbit of Mars with a circular orbit, what is the NAME of this step in the development of Kepler's theory of planetary motion?

The discrepancy between the old theory and the new observations was the problem that Kepler had to solve, that is, he needed to make a new model. (3 points)

6. List TWO TESTS of Copernicus' Model of the Solar System. (3 points each)

(1) Observation that Venus exhibits all phases from new to full.

(2) Observation of parallax of nearby stars.

(3) Observation that Jupiter has moons that orbit around it

(4) Abberation of starlight

(5) Foucault pendulum (shows rotation of the Earth)

(6) Coriolis effect (shows rotation of the Earth)

Visions of the Universe