Table of contents

2. 1D Motion / Kinematics

Intro to Acceleration

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Multiple Choice

The brakes of your car can provide an acceleration of 4.6m/s². You're speeding at 37.5 m/s and suddenly see a police car, so you slam the brakes. How long will it take for your car to slow down to the speed limit of 25 m/s?

0.37 s

33 s

2.7 s

Verified step by step guidance

Identify the initial speed of the car, \( v_i = 37.5 \text{ m/s} \), and the final speed, \( v_f = 25 \text{ m/s} \).

Recognize that the car is decelerating, so the acceleration \( a = -4.6 \text{ m/s}^2 \) (negative because it's slowing down).

Use the kinematic equation for constant acceleration: \( v_f = v_i + a \cdot t \), where \( t \) is the time it takes to slow down.

Rearrange the equation to solve for time \( t \): \( t = \frac{v_f - v_i}{a} \).

Substitute the known values into the equation: \( t = \frac{25 \text{ m/s} - 37.5 \text{ m/s}}{-4.6 \text{ m/s}^2} \) and solve for \( t \).

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The brakes of your car can provide an acceleration of 4.6m/s2. You're speeding at 37.5 m/s and suddenly see a police car, so you slam the brakes. How long will it take for your car to slow down to the speed limit of 25 m/s?