#### (a) By taking the slope of the curve in Figure 2.60, verify that the velocity of the jet car is 115 m/s at t = 20 s.

#### (b) By taking the slope of the curve at any point in Figure 2.61, verify that the jet car’s acceleration is 5.0 m/s².

**Solution:**

**Part A**

Based from the graph shown in figure 2.60, we can choose two points, one before and one after t=20 s. We have the points .

The slope is computed using the formula:

Therefore, we have verified that the velocity of the jet car is 115 m/s at t=20 seconds.

**Part B**

Since the graph is a straight line, we can use any two points to determine the slope of the line. The slope of the velocity-time graph is the acceleration.

The two points are

The acceleration is computed as

Therefore, the acceleration is verified to be 5.0 m/s².