a motorist travels with a constant speed of 20 m/s for 15 seconds. he then accel

Question

a motorist travels with a constant speed of 20 m/s for 15 seconds. he then accelerates at 3 m/s2 for 8 seconds to reach his desired top speed. He drives at this top speed for 35s and then takes another 18 seconds to bring the car to a full stop. calculate the total distance traveled & calculate the average speed for the trip. a motorist travels with a constant speed of 20 m/s for 15 seconds. he then accelerates at 3 m/s2 for 8 seconds to reach his desired top speed. He drives at this top speed for 35s and then takes another 18 seconds to bring the car to a full stop. calculate the total distance traveled & calculate the average speed for the trip. a motorist travels with a constant speed of 20 m/s for 15 seconds. he then accelerates at 3 m/s2 for 8 seconds to reach his desired top speed. He drives at this top speed for 35s and then takes another 18 seconds to bring the car to a full stop. calculate the total distance traveled & calculate the average speed for the trip.

Explanation / Answer

while travelling with constant speed ,distance travelled ,

20m/s * 15 = 300m

then while accelerating ,at 3m/s2 for 8 secs , distance covered ,

S=ut +0.5at2

= 20*8 +0.5*3*(8)2

=160+ 96

=256 m

the speed attained = v= u+at

= 20+3*8

= 44 m/s(top speed )

now ,

distance travelled at top speed,

44* 35 = 1540 m

distance travelled whie deaccelerating ,

a= 44 -0 / 18 = -2.4 m/s2

v2- u2 = 2as

02 - 442 = 2*(-2.4) *S

=>S= 322.66 m

so total distance ,

=300+256+ 1540 + 403.33 = 2243.33m

ttotal time = 15 + 8+ 35 + 18 secs

= 76 secs

so , avrage speed = total distance /total time = 29.52 m/s

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