The figure shows the speedometer readings as a car comes to a stop. Solve graphically for the acceleration a_x at t = 7.0 s. A) 2.5 m/s² B) − 2.5 m/s² C) − 2.0 m/s² D) 2.0 m/s²

Question

Quizplus · Accepted Answer

To solve for acceleration, we need to use the equation: 
a = (v_f - v_i) / t

At t = 7.0 s, the speed of the car is approximately 15 m/s. We can find the initial speed by looking at the graph, which is approximately 39 m/s.

Plugging in the values, we get: 
a = (15 m/s - 39 m/s) / 6 s = -4 m/s^2

However, this is the acceleration of the car, not the acceleration of the speedometer needle. To find the acceleration of the speedometer needle, we need to look at the slope of the tangent to the graph at t = 7.0 s.

Drawing a tangent line to the curve at t = 7.0 s, we can see that it has a slope of approximately -2.5 m/s^2. This is the acceleration of the speedometer needle, but it is in the negative direction because the speedometer is decreasing.

Therefore, the answer is B) -2.5 m/s^2.

The Figure Shows the Speedometer Readings as a Car Comes