Question

Numbers 2-4

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2. motorist drives east for 30 minutes at 85 km/hr and then stops for 15 minutes. He ihe continues east for another hour at 100 km/hr. What was his average velocity? .A motorist drives east for 30 minutes at 85 km/hr and then stops for 15 minutes. He then furns north and drives another hour at 100 km/hr. What was his average velocity? 4. A car travels 50 m up a hill n .o s while slowing down to a final velocity of 4.5 m/s. What was the car's initial velocity?

Answer 1

For first 30 minutes velocity = 85 km/h Total displacement = 85 times 30/60 = 72.5 km For next 15 minutes the motorist is at rest so displacement = 0 For next 1 hr velocity = 100 km/h displacement = 100 km/h times 1 h = 100 km Total displacement = (42.5 + 100) km = 142.5 km Total time = (30 + 15 60)min = 105 min = 105/60 = 1.75 hr average velocity = Total displacement/Total time = 142.5/1.75 = 81.428 km/h \r\n For first 30 minutes velocity = 85 km/h Displacement = 85 times 30/60 = 42.5 km Then he waits for 15 minutes i.e. displacement = 0 for next 1 hour he travels North with velocity = 100 km/h displacement = 100 km net displacement during the whole journey AN = squareroot (4.25)^2 + (100)^2 = 108.66 km average velocity = 108.66/1.75 = 62.1 km/hr \r\n Given final velocity v = 4.5 m/s time = t