# (solution) 1. A rock is dropped off the side of a bridge and hits the water

1. A rock is dropped off the side of a bridge and hits the water below8.9s later.

(a) What was the rock’s velocity when it hit the water?

(b) What was the rock’s average velocity as it fell?

(c) What is the height of the bridge above the water?

2. During takeoff, an airplane goes from 0 to82m/s in10s.

(a) What is its acceleration?

(b) How fast is it going after4s?

(c) How far has it traveled by the time it reaches82m/s?

3.A high-performance sports car can go from 0 to 100 mph in5.0s. (Assume the car travels in the positive direction. Indicate the direction with the sign of your answer.)

(a) What is the car’s average acceleration (in SI units; meter-kilogram-second)?

(b) The same car can come to a complete stop from 27 m/s in 6.1 s. What is its average acceleration?

4. A passenger jet flies from one airport to another 1,373 miles away in 2.1 h. Find its average speed in the mks system of units.

5. What are the “basic” or “fundamental” physical quantities? (Select all that apply.)

time

distance

area

mass

speed

(a) Why are they called that?

6. List the physical quantities identified in this chapter. From which of the fundamental physical quantities is each derived? Which of them are vectors, and which are scalars?

7. What is the distinction between speed and velocity? Describe a situation in which an object’s speed is constant but its velocity is not. 