Question

1 Speed and acceleration (a) (5 pts) Convert a speed of 88.5km/h into meters per second. (b) (10 pts) If your car accelerates from rest at a steady rate of 4m/s, how soon will it reach a speed of 10m/s? (c) (10 pts) If your car slows goes from a positive velocity of 20m/s to a full stop in 5 s, what is the acceleration include the sign)?

Answer 1

We know that 1 km = 1000 m 1h = 3600 second a) speed (v) = 88.5 km/h = 88.5 times 1000/3600 m/s = 24.58 m/s b) initially car is at rest so u initial speed u = 0 acceleration (a) = 4 m/s^2 final speed v = 10 m/s \r\n Because v = u + at substituting values v, u, a = > t = v - u/a = 10 - 0/4 = 2.5 s c) since car down so v = u + at v - u/t = +a substituting values 0 - 20/5 = a v = 0 m/s u = 20 m/s t = 5s a = -4 m/s^2
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