Question

Ken is driving down the road when a car suddenly pulls out in front of him. He applies the brake sharply and his car goes into a skid. While the car skids, it decelerates at a constant rate of 15 meters / sec2. If the car skids for 80 meters before stopping, how fast was Ken driving before he hit the brakes?

Answer 1

Answer:Ken's speed before he hits the brakes is 48.99m/s

Explanation:

Total distance covered by Ken's car during skidding is 80 meters. So S = 80. The car decelerates at a constant rate of 15 meters / sec^2. This rate would be - 15m/s because the velocity was reducing. The final velocity of the car,V would be zero. This is so because the car is coming to rest.

We want to determine how fast Ken was driving before he hit the brakes. This becomes initial velocity, U

We would apply Newton's equation of motion,

V^2 = U^2 + 2aS

0^2 = U^2 + 2 × - 15 × 80

0 = U^2 -2400

U^2 = 2400

U = √2400 = 48.99m/s