Module #9

Question 1

Vector Quantity

Answer 1

A physical measurement that contains directional information

Question 2

Scalar Quantity

Answer 2

A physical measurement that does not contain directional information

Question 3

Acceleration

Answer 3

The time rate of change of an object’s velocity

Question 4

Free Fall

Answer 4

The motion of an object when it is falling solely under the influence of gravity

Question 5

If an object’s poses shin does not change relative to a reference point, is it in motion relative to that reference point?

Answer 5

No. It is not moving relative to that reference point.

Question 6

A glass of water sits on a counter. Is it in motion?

Answer 6

The glass of water is moving relative to many reference points.

Question 7

A child is floating in and inner tube on a still lake. His position does not change relative to a tree on the shore. He watches two girls jog along the shore of the lake. The girls are keeping perfect pace with each other. Neither is pulling ahead nor falling behind the other.

(a) Relative to whom is the child in motion?
(b) Relative to whom is the first girl in motion?
(c) Relative to whom is the second girl not in motion?

Answer 7

(a) The child is in motion relative to the two girls.
(b) The first girl is in motion relative to the child.
(c) The second girl is motionless relative to the first girl.

Question 8

What is the speed of a boat that travels 10 miles in 30 minutes? Please answer in the miles per hour.

           distance traveled   Speed= ----------------
              time traveled

Answer 8

20 mi/hr

Question 9

What is the speed of a jogger who jogs 6 km in 45 minutes? Please answer in meters per second.

Answer 9

2.2 m/sec

Question 10

Label each quantity as a factor or scaler quantity. Also, identify it as speed, distance, velocity, acceleration, or none of these.

(a) 10 meters
(b) 1.2 meters/second2 east
(c) 3.4 feet/hour and slowing
(d) 56 liters
(e) 2.2 miles/minute west
(f) 2.2 millimeters/year

Answer 10

(a) Scalar quantity. Units indicate speed.
(b) Vector quantity. Acceleration .
(c) Scalar quantity. Units indicate speed.
(d) Scalar quantity. None of these.
(e) Vector quantity. Velocity.
(f) Scalar quantity. Units indicate speed.

Question 11

A car and a truck are traveling north on a highway. The truck has a speed of 45 mph and the car has a speed of 57 mph. If the truck is ahead of the car, what is the relative velocity?

Answer 11

12 mph towards each other

Question 12

It’s an object travels for 15 minutes with a constant velocity of 12 mph west, what is the acceleration?

Answer 12

The acceleration is zero

Question 13

A sports car goes from a velocity of zero to a velocity of 12 meters per second East in two seconds. What is the cars acceleration?

Answer 13

6 meters per second2 East

Question 14

A train takes a long time to stop. That’s what makes train so dangerous to people who cross the tracks when one is near. If a train is traveling at 30 mph south and takes 12 minutes to come to a stop, what is the trains acceleration?

Answer 14

150 mph2 north

Question 15

A very picky physicist states that it is impossible for any object to experience free fall near the earth’s surface. Why is the physicist technically correct?

Answer 15

Air resistance is a second influence, and all objects experience air resistance.

Question 16

Why do we go ahead and assume that heavy objects are in freefall when they fall near the surface of the earth?

Answer 16

The effects of air resistance is so small on heavy objects that it usually can be ignored.

Question 17

A long, vertical glass tube contains a feather and a penny. All the air is pumped out, and the tube is inverted, causing the penny and feather to fall. Which hits the bottom first, the feather or the penny?

Answer 17

Neither will hit first. They both hit together.

Question 18

What is the height of a building (in meters) if it takes a dropped rock 4.1 seconds to fall from its roof?

Answer 18

82.4 m

Question 19

A hot air balloon just drops a rock from his balloon. It takes seven seconds for the rock to fall to the ground. What is the balloonist’s altitude in feet?

Answer 19

784 feet

Question 20

A scientist decides to study the acceleration of an object moving in a straight line. He measures the distance the object travels in
30-second time intervals. The scientist notices that in each interval the object travels a shorter distance than it did in the previous interval. Is the direction of the acceleration the same as or opposite of the velocity?

Answer 20

Opposite direction

Question 21

Reference Point

Answer 21

A point against which position is measured