Problem 22
Calculate In 2009, Usain Bolt of Jamaica set a world record of \(9.58 \mathrm{~s}\) in the \(100-\mathrm{m}\) dash. What was his average speed? Give your answer in meters per second and kilometers per hour.
Problem 24
Think \& Calculate A train travels in a straight line at \(20.0 \mathrm{~m} / \mathrm{s}\) for \(2 \mathrm{~km}\), then at \(30.0 \mathrm{~m} / \mathrm{s}\) for another \(2 \mathrm{~km}\). (a) Is the average speed of the train greater than, less than, or equal to \(25 \mathrm{~m} / \mathrm{s}\) ? Explain. (b) Verify your answer to part (a) by calculating the average speed.
Problem 26
A rose-covered parade float is at \(x=0\) at time \(t=0\). The float moves in a straight line at \(2.0 \mathrm{~m} / \mathrm{s}\) for the next \(5 \mathrm{~s}\) before coming to a stop. After a 5 -s stop, the float moves again at \(1.0 \mathrm{~m} / \mathrm{s}\) in the same direction as before. (a) Sketch the position-time graph for the float from the time \(t=0\) until the time \(t=15 \mathrm{~s}\). (b) From your graph, determine the positions of the float at \(t=2 \mathrm{~s}\) and \(t=11 \mathrm{~s}\).
Problem 27
\(-\) Identify What physical quantities are measured along the axes of a position-time graph?
Problem 28
Explain What does the slope of a positiontime graph tell you about the motion of an object?
Problem 29
Big ldea What does the position-time graph look like for an object moving with constant velocity?
Problem 29
Bigldea What does the position-time graph look like for an object moving with constant velocity?
Problem 35
The position-time equation of motion for a bunny hopping across a yard is $$ x_{\mathrm{f}}=8.3 \mathrm{~m}+(2.2 \mathrm{~m} / \mathrm{s}) t $$ (a) What is the initial position of the bunny? (b) What is the bunny's velocity? 36\. A bowling ball moves with constant velocity from an initial position of \(1.6 \mathrm{~m}\) to a final position of \(7.8 \mathrm{~m}\) in \(3.1 \mathrm{~s}\). (a) What is the position-time equation for the bowling ball? (b) At what time is the ball at the position \(8.6 \mathrm{~m}\) ?
Problem 36
A bowling ball moves with constant velocity from an initial posi- tion of \(1.6 \mathrm{~m}\) to a final position of \(7.8 \mathrm{~m}\) in \(3.1 \mathrm{~s}\). (a) What is the position-time equation for the bowling ball? (b) At what time is the ball at the position \(8.6 \mathrm{~m}\) ?
Problem 39
You are riding in a car on a straight stretch of a two-lane highway with a speed of \(26 \mathrm{~m} / \mathrm{s}\). At a certain time, which we will choose to be \(t=0\), you notice a truck moving toward you in the other lane. The truck has a speed of \(31 \mathrm{~m} / \mathrm{s}\) and is \(420 \mathrm{~m}\) away at \(t=0\). (a) Write the position-time equations of motion for your car and for the truck in the other lane. (b) Plot the two equations of motion on a position-time graph. (c) At what time do you and the truck pass one another, going in opposite directions?
