Shone all work including formidas used to receite full cvedit Answers must have

Question

Shone all work including formidas used to receite full cvedit Answers must have appropriate units. 1. A person travels by car from Tucson to Phoenix at a constant speed of 75 km/hr. They then retum from Phoenix to Tucson at a constant speed of 65 km/hr. What was their average velocity? 2. A motorist drives east for 45 minutes at 75 km/hr and then stops for 15 minutes. He ther continues east for another hour at 100 km/hr. What was his average velocity? A motorist arives east for 45 minutes at 75 km/hr and then stops for 15 minutes. He then turns north and drives another hour at 100 km/hr. What was his average velocity'? 3. A car travels 50.0 m up a hill in 9.0 s while slowing down to a final velocity of 4.7 m/s. What was the car's initial velocity?

Explanation / Answer

Q1:

Assume distance from Tucson to phoenix = x km

time taken for Tucson to phoenix = x/75 hr

time taken for phoenix to Tucson = x/65 hr

Total time = x/75 + x/65

average speed = total distance/total time

average speed = 2x/( x/75 + x/65)

average speed = 2x/( 140x/4875)

average speed = 69.64 km/h

Q2:

Distance travelled in 45 minutes = (75/60)*45 = 56.25 km

distance covered in second run = 100 km

total distance = 156.25 km

Avg. speed = 156.25/2 = 78.125 km/h

Q3:

Going East Distance travelled in 45 minutes = (75/60)*45 = 56.25 km

Going North distance travelled = 100 km

distance between start and end point:

D = sqrt(56.252 + 1002)

D = 114.7347 km

avg. speed = 114.7347/2 = 57.36 km/h

Q4:

we know

v = u + at

4.7 = u + a*9

a = (4.7 – u)/9

put the value of a in,

v2 – u2 = 2as

4.72 – u2 = 2*{(4.7 – u)/9}*50

22.09 – u2 = 52.2222 – 11.111u

u2 - 11.111u + 30.132

u = 6.41 m/s

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