The answers are easy to check. An alternate technique is to use Delta x = v_0t +

Question

The answers are easy to check. An alternate technique is to use Delta x = v_0t + 1/2 at^2 to find t and then use the equation v = v_0 + at to find v. Notice that the two different equations for calculating the average velocity, due to rounding, give slightly different answers. What is the final speed if the displacement is increased by a factor of 4? 35 m/s Use the worked example above to help you solve this problem. A race car starting from rest accelerates at a constant rate of 6.80 m/s^2. What is the velocity of the car after it has traveled 1.30 times 10^2 ft? _______ m/s Suppose the driver in this example is now moving with speed 38.6 m/s, and slams on the brakes, stopping the car in 4.6 s. (a) Find the acceleration assuming the acceleration is constant. _______ m/s^2 (b) Find the distance the car travels, assuming the acceleration is constant. _______ m (c) Find the average velocity. _______ m/s

Explanation / Answer

Practice It:

Initial velocity,u=0

Final velocity=v

acceleration = a=6.8 m/s2

distance travelled = s=130 ft = 9.144m

v2=u2+2as = 0 + (2*6.8*9.144) = 124.3584

v = sqrt(124.3584) = 11.15 m/s

Exercise:

a)Intial speed = 38.6 m/s

Time taken to stop car = 4.6 s

acceleration = (0-38.6)/4.6 = -8.39 m/s2 (negative sign is because the car is decelerating)

b)S=ut+(1/2)at2 = (38.6*4.6)+(1/2)*(-8.39)*(4.62) = 88.79m

c)Averate velocity = distance travelled/time taken = 88.79/4.6 = 19.3 m/s

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