1. A car travelling along a straight road at 20 km/h begins to gradually increas

Question

1. A car travelling along a straight road at 20 km/h begins to gradually increase its speed and after 4 seconds it is travelling at 50 km/h. What is the acceleration of that car, in m/s/s? (Consult Table 3.1 in your text for unit conversion

2. A car traveling along a straight road at 30 km/h begins to gradually increse its speed and after 4.0 seconds it reaches the speed of 40 km/h. What was the acceleration of that car, in

3 . ou toss-up a ball straight up and it leaves your hand at a speed of 20 m/s. How high, in meters, will it rise above the release point? Assume g = 10 m/s/s.

4. You toss-up a ball straight up and it leaves your hand at a speed of 15 m/s. After what time, in seconds, will it return to your hand? Assume g = 10 m/s/

Explanation / Answer

1) initial speed is u = 20 km/h = 20*5/18 = 5.55 m/s
final speed is v = 50 km/h = 50*5/18 = 13.89 m/s

time taken is t = 4 S

accelaration a = (v-u)/t = (13.89-5.55)/4 = 2.085 m/s^2

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2) u = 30*5/18 = 8.34 m/s

v = 40*5/18 = 11.12 m/s

t = 4 S

accelaation a = (v-u)/t = (11.12-8.34)/4 = 0.695 m/s^2

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3) height reached by the ball H = u^2/(2*g) = (20^2)/(2*10) = 20 m
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4) time of flight T = 2*u/g = 2*15/10 = 3 S

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