Question

A speeding car sees a deer and slams on its brakes. It changes its speed from 30 m/s to zero with an acceleration of -3 m/s^2. How long does it take the car to stop?

a) 10 seconds
b) 15 seconds
c) 20 seconds
d) 30 seconds

Answer 1

Using the kinematic equation, the car takes 10 seconds to stop when decelerating at -3 m/s² from 30 m/s to 0.

Step-by-step explanation:

When a car slams on its brakes and changes its speed from 30 m/s to 0 with an acceleration of -3 m/s2, we can calculate the time it takes to stop using the kinematic equation t = (v - u) / a, where 'v' is the final velocity, 'u' is the initial velocity, and 'a' is the acceleration. Plugging in the values, we get t = (0 - 30) / (-3), which simplifies to t = 30 / 3, giving us t = 10 seconds. Therefore, the correct answer is (a) 10 seconds.