A car traveling at an initial speed \(v_0\) begins braking. The deceleration is not constant but increases linearly with time, modeled by \(a(t) = -kt\), where \(k\) is a positive constant.
(a) Derive an expression for the velocity \(v(t)\) of the car as a function of time \(t\), given the initial velocity \(v(0) = v_0\). Then, set up a definite integral that represents the distance traveled by the car from the moment braking begins until the car comes to a complete stop. (Hint: First, find the stopping time by determining when the velocity becomes zero.)
(b) For a car with an initial speed of 30 m/s and a deceleration constant \(k = 1\;m/s^3\), calculate the stopping time and the stopping distance using the integral expression from part (a). Provide your answers with appropriate units and to three significant figures.
Question
Derive the velocity function \(v(t)\) from the acceleration \(a(t)= -kt\) given \(v(0)=v_0\). Use this velocity function to determine the stopping time, and then set up the definite integral for the stopping distance, representing the distance traveled from \(t=0\) until the car stops.
Hint
Hint
Hint
Integrate \(a(t)\) to find \(v(t)\). Set \(v(t) = 0\) to find the stopping time \(t_s\). The stopping distance is given by \(\int_{0}^{t_s} v(t)\,dt\).
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Answer
Answer
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Explanation
Explanation
- Formula Booklet
Complete Answer
Velocity function: \(v(t) = v_0 – \frac{k t^2}{2}\). Stopping time: \(t_s = \sqrt{\frac{2v_0}{k}}\). Stopping distance integral: \(\int_{0}^{\sqrt{2v_0/k}} \Big(v_0 – \frac{k t^2}{2}\Big)\,dt\).
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Answer Explanation
Answer Explanation
Question
Using \(v_0 = 30\;m/s\) and \(k = 1\;m/s^3\), calculate the stopping time and evaluate the integral to determine the stopping distance. Give your answers to three significant figures and include units.
Hint
Hint
Hint
Substitute \(v_0 = 30\) and \(k = 1\) into the expressions for stopping time and stopping distance integral from part (a). Use your GDC to evaluate the definite integral.
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Answer
Answer
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Explanation
Explanation
- Formula Booklet
Complete Answer
Stopping time \(t_s = \sqrt{60} \approx 7.75\;s\). Stopping distance \(s = 154.919… \approx 155\;m\).
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Mark Scheme
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Answer Explanation
Answer Explanation