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CBSE Class 9 Answered

A car of mass 1500 kg is moving with a a velocity of 50 kilometre per hour and travel a distance 90 km in 2 hours . Find its acceleration and force produced by it.
Asked by gangaramgourkar23 | 16 Jul, 2019, 05:56: PM
answered-by-expert Expert Answer
It is assumed, initially the car travels with speed 50 km/h.
 
It is given that it has travelled 90 km in 2 hour, hence its average speed is 45 km/hr .
 
Since initial speed is 50 km/hr , then we consider that  speed is decreased to 40 km/hr after 2 hour,
so that we get average speed 45 km/hr.
 
initial speed u,  50 km/hr  = 50× (5/18) m/s ≈ 13.9 m/s
final speed v, 40 km/hr = 40×(5/18) ≈ 11 m/s
 
acceleration  a = (v-u)/t = (11-13.9)/(2×60×60) ≈ - 4.0×10-4 m/s2
 
force applied to reduce the speed = mass×acceleration = 1500×4.0×10-4 = 0.6 N
Answered by Thiyagarajan K | 17 Jul, 2019, 10:05: AM

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