A sports car accelerates approximately as shown in the velocity-time graph of Fig. 2-43. (The short flat spots in the curve represent manual shifting of the gears.) Calculate the car's average acceleration in (a) second gear.

Figure 2-42 shows the velocity of a train as a function of time. At what time was its velocity greatest?

When an object moves with constant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any instant?

A particle at $t_1=-2.0 \mathrm{~s}$ is at $x_1=5.2 \mathrm{~cm}$ and at $t_2=3.4 \mathrm{~s}$ is at $x_2=8.5 \mathrm{~cm}$. What is its average velocity over this time interval? Can you calculate its average speed from these

You drive $4 \mathrm{~km}$ at $30 \mathrm{~km} / \mathrm{h}$ and then another $4 \mathrm{~km}$ at $50 \mathrm{~km} / \mathrm{h}$. What is your average speed for the whole $8-\mathrm{km}$ trip? (a) More than $40\ \mathrm{km/h}$ (b) Equal to $40 \mathrm{~km} / \mathrm{h}$. (c) Less than $40 \mathrm{~km} / \mathrm{h}$. (d) Not enough information.

The position of a racing car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate its acceleration as a function of time. Display each in a Table and on a graph.

$$\begin{matrix} \text{t (s)} & \text{0} & \text{0.25} & \text{0.50} & \text{0.75} & \text{1.00} & \text{1.50} & \text{2.00} & \text{2.50}\\ \text{x (m)} & \text{0} & \text{0.11} & \text{0.46} & \text{1.06} & \text{1.94} & \text{4.62} & \text{8.55} & \text{13.79}\\ \text{t(s)} & \text{3.00} & \text{3.50} & \text{4.00} & \text{4.50} & \text{5.00} & \text{5.50} & \text{6.00} & \text{ }\\ \text{x(m)} & \text{20.36} & \text{28.31} & \text{37.65} & \text{48.37} & \text{60.30} & \text{73.26} & \text{87.16} & \text{ }\\ \end{matrix}$$