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4. A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus. |
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Answer» ecreases its speed from 80 km/h to 60 km/h in 5 s. Given that, starting speed means the initial velocity (U) of the bus is 80 km/hr.And ending or final velocity (v) of the bus is 60 km/hr.Also given that, time (t) is 5 seconds.We have to find the ACCELERATION of the bus. Using First Equation of Motion i.e.v = u + atGiven time is in seconds and speed is in km/hr. So, CONVERT the speed in m/s.Initially velocity (u) = 80 × 5/18 = 22.22 m/sFinal velocity (v) = 60 × 5/18 = 16.67 m/sSubstitute them in the above formula→ 16.67 = 22.22 + a(5)→ 16.67 - 22.22 = 5a→ -5.55 = 5a→ -1.11 = a(Negative SIGN shows the deceleration or retardation)Therefore, the deceleration of the bus is -1.11 m/s². |
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