Problem 12
The red kangaroo (Macropus rufus, shown in Figure 2.5) is the largest marsupial in the world. It has been clocked hopping at a speed of \(65 \mathrm{~km} / \mathrm{h}\). (a) How far (in kilometers) can a red kangaroo hop in \(3.2\) minutes at this speed? (b) How much time will it take the kangaroo to hop \(0.25 \mathrm{~km}\) at this speed?
Problem 13
Challenge A finch rides on the back of a Galapagos tortoise, which walks at the stately pace of \(0.060 \mathrm{~m} / \mathrm{s}\). After \(1.2\) minutes the finch tires of the tortoise's slow pace, and it takes flight, traveling in the same direction for another \(1.2\) minutes at \(13 \mathrm{~m} / \mathrm{s}\). What was the average speed of the finch over the entire \(2.4\)-minute interval?
Problem 15
Concept Check After a tennis match the two players dash to the net to shake hands. If they both run with a speed of \(3 \mathrm{~m} / \mathrm{s}\), are their velocities equal? Explain.
Problem 16
In a well-known novel a person travels around the world in 80 days. (a) What is the person's approximate average speed during the adventure? (b) What is the approximate average velocity for the entire trip? (Note that Earth's circumference at the equator is \(40,075 \mathrm{~km}\).)
Problem 17
Rank Four trains travel on different sections of a long straight track. Taking north to be the positive direction, rank the trains in order by velocity, from most negative to most positive. The trains move as follows: Train A moves north with a speed of \(10 \mathrm{~m} / \mathrm{s}\). Train B heads south and covers \(900 \mathrm{~m}\) in \(1 \mathrm{~min}\). Train \(\mathrm{C}\) also heads south and has twice the speed of train \(A\). Train D travels north and covers \(24 \mathrm{~m}\) in \(2 \mathrm{~s}\).
Problem 18
Concribe What is the main difference between velocity and speed?
Problem 18
Describe What is the main difference between velocity and speed?
Problem 19
State What are the SI units of speed?
Problem 20
Analyze Friends tell you that on a recent trip their average velocity was \(+20 \mathrm{~m} / \mathrm{s}\). Is it possible that at any time during the trip their velocity was \(-20 \mathrm{~m} / \mathrm{s}\) ? Explain, and give an example to justify your answer.
Problem 21
Triple Choice Suppose you ride a bicycle around the block, returning to your starting point. At the end of your trip, is your average speed greater than, less than, or equal to the magnitude of your average velocity? Explain.
