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A car stops in 20 m. If it has an acceleration of -6 m/s^2, how fast was it going before it started slowing down?

a) 6m/s
b) 8m/s
c) 12m/s
d) 10m/s

User Hershi
by
8.7k points

1 Answer

2 votes

Final answer:

Using the kinematic equation v² = u² + 2as with the given acceleration of -6 m/s² and stopping distance of 20 m, the initial speed (u) turns out to be approximately 15.49 m/s, which is not listed in the provided options.

Step-by-step explanation:

To determine how fast a car was going before it started slowing down with an acceleration of -6 m/s² and stops in 20 m, we can use the kinematic equation: v² = u² + 2as, where:

  • v is the final velocity (0 m/s since the car stops)
  • u is the initial velocity (what we are trying to find)
  • a is the acceleration (-6 m/s²)
  • s is the distance (20 m)

Substituting the given values into the equation: 0 = u² + 2(-6)(20).

Solving for u:

u² = 240

u = √240

u = approximately 15.49 m/s

However, this speed is not one of the provided options (a-d). There's either a mistake in the problem or in the proposed answers.

User Aresnick
by
8.4k points
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