Engineering Physics Wave motion and Mechanics

Question

Julie drives 100  to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 40.0  and half the distance at 60.0  . On her return trip, she drives half the time at 40.0  and half the time at 60.0 

Part A- What is Julie's average speed on the way to Grandmother's house?

Part B- What is her average speed on the return trip?

Answer 1

Hello Kerriannedj

I assume the total one way distance is 100 Km

half of this distance is covered at 40 Km/hr and remaining half at 60 Km/hr ( While going )

As Speed = distance /time

40 = 50/t1

and 60 = 50/t2

t1= 50/40 hr= 5/4 hr

and t2 = 50/60 = 5/6 hr

Thus average speed while going = Total distance/ total time= 100/( t1 +t2) = 100/( 5/4 +5/6)=(100*24)/50 = 48 km/hr

( you may change units to miles /hr , if speed and distance are given in mile/hr and miles)

Like wise try the part 2 for return trip

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