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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.

Respuesta :

Answer:

Explanation:

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 .

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