Answer to Question #235819 in Physics for Maskeen

Question #235819

you drive your car in a straight line at 15 m/s for 10 minutes then at 25 m/s for another 10 minutes. is your average speed for entire trip more than, less than or equal to 20 ms

1
Expert's answer
2021-09-12T19:01:34-0400

By definition, the average speed is given as total distance divided by total time:


vav=d1+d2t1+t2v_{av} = \dfrac{d_1+d_2}{t_1 + t_2}

where d1,d2d_1,d_2 are the parts of total distance covered during times t1=10min=600s,t2=10min=600st_1 = 10min = 600s,t_2 = 10min = 600s with speeds v1=15m/s,v2=25m/sv_1 = 15m/s, v_2 = 25m/s respectively.

For the first half of the journey, obtain:


d1=v1t1d_1 = v_1t_1

For the second half:


d2=v2t2d_2 = v_2t_2

Finally, obtain:


vav=v1t1+v2t2t1+t2=15600+25600600+600=20m/sv_{av} = \dfrac{v_1t_1+v_2t_2}{t_1 + t_2} = \dfrac{15\cdot 600+25\cdot 600}{600 + 600} = 20m/s

Answer. equal to 20 m/s.


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