1.A vertical stick in sunlight casts a shadow. But it will y cast no shadow if located at a point on Earth's surface & where the Sun is directly overhead. A second vertical

stick about a hundred kilometers due north of the first

one simultaneously casts a shadow that points

A. northward.

B. southward.

C. slightly eastward of a north-south line.

D. slightly westward of a north-south line.

E. none of the above.

This is remindful of Eratosthenes' measurement of Earth's size back in about 235 B.C.

2.Three equal-length metal strips are bent and forme into racing tracks. The humped curve is the inverse the dipped curve. When balls are simultaneously released, the first to reach the end of its track is

A. Ball A.

B. Ball B.

C. Ball C.

D. All the same.

The ball to finish with the greatest speed is

E. Ball A.

F. Ball B.

G. Ball C.

H. All the same.

Concept of Force

Why is force a vector quantity?

Aforce has a magnitude, but not a direction.

A force has a magnitude and a direction.

A force is measured in pounds, and pounds are a vector quantity.

A force is a scalar quantity.

Force is a vector

What is the net force on an object that is pulled with 80 N to the right and 80 N to the left?

The net force is zero newtons.

The net force is 160 newtons to the right.

The net force is 113 newtons downward.

The net force is 113 newtons upward.

What is the net force on a bag pulled down by gravity with 18 N and pulled upward by a rope with 18 N?

The net force is zero newtons.

The net force is 36 newtons.

The net force is 25 newtons.

The net force is 18 newtons.

PartA

A 12-N book is at rest on a flat table. How many newtons of support force does the table provide?

12 newtons up

0 newtons

24 newtons up

12 newtons down

Part B

What is the net force on the book?

12 newtons up

0 newtons

12 newtons down

24 newtons up

Concept of Inertia

- Your friend says that inertia is a force that keeps things in their place, either at rest or in motion. Do you agree? Why or why not?

(conduct a short paragraph to justify your answer)

-When you push a cart, it moves. When you stop pushing, it comes to rest. Does this violate Newton's law of inertia? Defend your answer.

- Before the time of Galileo and Newton, some learned scholars thought that a stone dropped from the top of a tall mast of a moving ship would fall vertically and hit the deck behind the mast by a distance equal to how far the ship had moved forward while the stone was falling.

In light of your understanding of Newton's first law, what do you think about this?

Understanding Friction

If you push on a crate with a horizontal force of 120 N and it slides at constant velocity, how much is the friction acting on the crate?

The frictional force has nothing to do with you pushing on the crate.

The frictional force on the crate is zero newtons.

The frictional force on the crate is 120 N opposite the direction of motion.

The frictional force on the crate is 120 N in the same direction as the direction of motion

Application of First Law

Description: A different scaffold that weighs 400 N supports two painters, one 500 N and the other 400 N. The reading in the left scale is 800 N. (a) What is the reading in the right-hand scale?

A different scaffold that weighs 400 N supports two painters, one 500 N and the other 400 N. The reading in the left scale is 800 N.

As you stand on a floor, does the floor exert an upward force against your feet? How much force does it exert? Why are you not moved upward by this force?