Question

A speeding truck slams on the brakes and accelerates at -7.20 m/s² before coming to a stop. It leaves skid marks on the pavement that are 49.1 m long. How fast was the truck going before it slammed on the brakes?

A) 7.20 m/s
B) 14.4 m/s
C) 36.0 m/s
D) 72.0 m/s

Answer 1

To find the initial velocity of the truck, we can use the kinematic equation and plug in the given values. The truck was going approximately 26.55 m/s before it slammed on the brakes.

Step-by-step explanation:

To solve this problem, we can use the kinematic equation:

vf^2 = vi^2 + 2aΔx

where:

• vf is the final velocity (0 m/s, since the truck comes to a stop)
• vi is the initial velocity (what we're trying to find)
• a is the acceleration (-7.20 m/s²)
• Δx is the displacement (49.1 m)

Plugging in the given values into the equation, we have:

0 = vi^2 + 2(-7.20)(49.1)

vi^2 = 2(7.20)(49.1)

vi^2 = 705.12

vi ≈ 26.55 m/s

Therefore, the truck was going approximately 26.55 m/s before it slammed on the brakes