College Physics

Figure 2.51Graphs of motion of a jet-powered car as it reaches its top velocity. This motion begins where the motion inFigure 2.48ends. (a) The slope of this graph is

velocity; it is plotted in the next graph. (b) The velocity gradually approaches its top value. The slope of this graph is acceleration; it is plotted in the final graph. (c) Acceleration

gradually declines to zero when velocity becomes constant.

Example 2.19 Calculating Acceleration from a Graph of Velocity versus Time

Calculate the acceleration of the jet car at a time of 25 s by finding the slope of thevvs.tgraph inFigure 2.51(b).

Strategy

The slope of the curve att= 25 sis equal to the slope of the line tangent at that point, as illustrated inFigure 2.51(b).

Solution

Determine endpoints of the tangent line from the figure, and then plug them into the equation to solve for slope,a.

(2.100)

slope =Δv

Δt

=

(260 m/s − 210 m/s)

(51 s − 1.0 s)

(2.101)

a=50 m/s

50 s

= 1.0 m/s^2.

Discussion

74 CHAPTER 2 | KINEMATICS

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