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Writer's picturekeshprad

PhysicsBowl 2019 Q33


33) This question asks us to consider two cars accelerating at different rates. One car starts two seconds after the first car. For this question, we want to find the time when the two cars pass each other.


We can start by setting up a kinematic equation for the distance covered by car 1.

Where d is distance, v is velocity, t is time, and a is acceleration

Next, let's set up an equation for the distance traveled by the second car. Instead of t, we will use (t-2) for time because this allows us to account for the second car starting to accelerate two seconds after the first car.

Where d is distance, v is velocity, t is time, and a is acceleration

We want to find the time at which the two cars pass each other, so we can equate these two equations and solve for t.

Where d is distance, and t is time

From the two solutions of the quadratic, the answer must be time t = 4. This is because at time t = 1.333 the second car hasn't even started moving, so it wouldn't make sense that the cars pass each other at this time.


Answer: B

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