A certain car is capable of accelerating at a rate of 0.65 m/s^2. How long does

Question

A certain car is capable of accelerating at a rate of 0.65 m/s^2. How long does it take for this car to go from a speed of 40 mi/h to a speed of 44 m/h? Your response differs from the correct answer by more than 100%. An object moving with uniform acceleration has a velocity of 13.0 cm/s in the positive x-direction when its x-coordinate is 2.70 cm. if its x coordinate 2.05 s later is -5.00 cm, what is its acceleration? of the object in one-dimensional motion at constant acceleration as function of time. Use the value of the expression at the two times the acceleration. cm/s^2

Explanation / Answer

Vf = final velocity, Vi = initial velocity, a = acceleration, t= time
You must convert to get everything into the same units, you cannot have miles/hour and m/s^2

40 miles/hour --> 17.8816 m/s
44 miles/hour --> 19.6698 m/s

Vf = Vi + at
rearrange for t
t = (Vf - Vi)/a
t = (19.668-17.8816)/(0.65)
t = 2.706 seconds

2...At time t=2s
x2 = -5cm

x = x2 - x0 = - 7.70 cm
t = 2 s

For constant acceleration, x = vt + ½ a(t)²

a = 2(x - vt) / (t)² = 2(-7.70 - 26)/4 = -16.85 cm/s²

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