2.2 The school bus picks up Brian in front of his house and takes him on a straight-line 2.1 km bus ride to school in the positive
direction. He walks home after school. If the front of Brian's house is the origin, (a) what is the position of the school, (b) what
is his displacement on the walk home, and (c) what is his displacement due to the combination of the bus journey and his
walk home?
(a) km
(b) km
(c) km
2.3 A strange number line is measured in meters to the left of the origin, and in kilometers to the right of the origin. An object
moves from í2200 m to 3.1 km. Find its displacement (a) in kilometers, and (b) in meters.
(a) km
(b) m
2.4 The Psychic Squishy Sounds band is on tour in Texas and now are resting in Houston. They traveled 60.0 miles due south
from their first concert to Huntsville. If Huntsville is 80.0 miles due north of Houston, what is their displacement from the first
concert to Houston? Use the convention that north is positive, and south is negative.
milesSection 3 - Velocity
3.1 To estimate the distance you are from a lightning strike, you can count the number of seconds between seeing the flash and
hearing the associated thunderclap. For this purpose, you can consider the speed of light to be infinite (it arrives instantly).
Sound travels at about 343 m/s in air at typical surface conditions. How many kilometers away is a lightning strike for every
second you count between the flash and the thunder?km
3.2 A jogger is moving at a constant velocity of +3.0 m/s directly towards a traffic light that is 100 meters away. If the traffic light is
at the origin, x = 0 m, what is her position after running 20 seconds?
m
3.3 A slug has just started to move straight across a busy street in Littletown that is 8.0 meters wide, at a constant speed of 3.3
millimeters per second. The concerned drivers on the street halt until the slug has reached the opposite side. How many
seconds elapse until the traffic can start moving again?
s
3.4 Light travels at a constant speed of 3.0×10^8 m/s in a vacuum. (a) It takes light about 1.3 seconds to travel from the Earth to
the Moon. Estimate the distance of the Moon from the Earth's surface, in meters. (b) The astronomical unit (abbreviated AU)
is equal to the distance between the Earth and the Sun. One AU is about 1.5×10^11 m. If the Sun suddenly ceased to emit
light, how many minutes would elapse until the Earth went dark?
(a) m
(b) minSection 4 - Average velocity
4.1 In 1271, Marco Polo departed Venice and traveled to Kublai Khan's court near Beijing, approximately 7900 km away in a
direction we will call positive. Assume that the Earth is flat (as some did at the time) and that the trip took him 4.0 years, with
365 days in a year. (a) What was his average velocity for the trip, in meters per second? (b) A 767 could make the same trip
in about 9.0 hours. What is the average velocity of the plane in meters per second?
(a) m/s
(b) m/s
4.2 An airport shuttle driver is assigned to drive back and forth between a parking lot (located at 0.0 km on a number line) and the
airport main terminal (located at +4.0 km). The driver starts out at the terminal at noon, arrives at the lot at 12:15 P.M., returns
to the terminal at 12:30 P.M., and arrives back at the lot at 12:45 P.M. What is the average velocity of the shuttle between (a)
noon and 12:15, (b) noon and 12:30, and (c) noon and 12:45? Express all answers in meters per second.
(a) m/s
(b) m/s
(c) m/s(^46) Copyright 2007 Kinetic Books Co. Chapter 2 Problems