### Physics

##### concept reinforcement quiz 3
Birth of Dynamics: Newton

Section 1: Development of the theory:

• Aristotle suggested that the earth is composed of four elementary substances, each with a natural place.   Indicate on a sketch where each substance belongs:

• What were Aristotle's views on motion and their causes?

• To Aristotle, some motions were natural, and required no cause.   Which were natural motions?  How were Newton's views different?

• In what time period did Aristotle live?

• In what ways was the culture of Newton's time different from Aristotle's?

• Define scalar:

• Define vector:

• What is dynamics?

• What is kinematics?

• How does a jet engine make a plane go forward?

• Certain kinds of motions are considered natural. Describe those Aristotle considered natural, and those Newton considered natural:

• Why does a sky diver "feel" weightless?

• Why does an orbiting astronaut "feel" weightless?

• The SI unit for force is:

• If for every force there is an equal but opposite force, how can anything possibly move?
Accurately draw the sum of each set of vectors below: Circle the pairs of vectors that are equal: In each of the six pairs of vectors above, find the difference between the top and bottom vectors (i.e., subtract).

Identify each of the following as vector, scalar, or other:
• a 20 knot wind blows out of the west

• SPEED LIMIT 55

• KEEP RIGHT

• travelling south at 2 p.m.

Section 2: Mathematical section: Apply your understanding by making specific predictions.  List all equations you use, and show substitutions and algebra.   Show your stepwise solution procedure.  Answers need to be reported with the correct uncertainty (i.e., the correct number of significant figures), and appropriate unit labels:

1. If a rock is dropped from a tall cliff on the moon where gravity is 0.165 that on earth, what will be the speed of the rock 9.0 seconds later?

2. The sun has a mass of 2.0 x 1030 kg; the earth has a mere mass of 6.0 x 1024 kg; still, the earths's gravitational pull on the sun is 1.4 x 1023 Newtons. What force does the sun's gravity pull on the earth?

3. Mountain View is 80  miles east and 100  miles south of Ocean Port. What is the air displacement Mountain View to Ocean Port? [Use a diagram to show direction.]

4. If a south wind is blowing steadily at 40 miles/hr, and a small airplane has an air speed of 120 miles/hr, draw a scale diagram and determine which direction will be needed to fly from Sequim to Seatac, a town due southeast?

5. What will a 50 kg person weight in an elevator acclerating upwards 1.0 m/s2? (I.e., what will be the force of the floor on this person?)  