2. The skid marks made by an automobile indicated that its breaks were first applied for a distance of 60 meters (m) before it came to a complete stop. The car in question is known to have a constant deceleration of 20 m/s2 under these conditions. How fast (in km/h) was the car traveling when the brakes were first applied? [Be sure to sketch your coordinate system to clarify the meaning of the functions involved.] Be sure to include units in your answer.

Question

Guest

Physics

16 September, 07:15

2. The skid marks made by an automobile indicated that its breaks were first applied for a distance of 60 meters (m) before it came to a complete stop. The car in question is known to have a constant deceleration of 20 m/s2 under these conditions. How fast (in km/h) was the car traveling when the brakes were first applied? [Be sure to sketch your coordinate system to clarify the meaning of the functions involved.] Be sure to include units in your answer.

+1

Answers (1)

Know the Answer?

Adan · Answer 1

We shall take motion along x - axis (positive)

We shall apply the equation of law of motion as follows

v² = u² - 2aS

v is final velocity, u is initial velocity, S is displacement and a is deceleration.

0 = u² - 2 x 20 x 60

u² = 2 x 20 x 60

u² = 2400

u = 49 m / s approx.

= 49 x 60 x 60 / 1000 km / h

= 176.4 km / h.