Solve a Simple Physics Problem: Boat Speed and River Flow in 30 Minutes

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SUMMARY

The discussion centers on calculating the time it takes for a boat to travel 12 km upstream in a river with a flow rate of 6.0 km/hr, given that the boat's speed in still water is 30 km/hr. The correct approach involves determining the boat's effective speed against the current, which is calculated as 30 km/hr - 6.0 km/hr = 24 km/hr. The time taken to cover the distance is then computed using the formula time = distance/speed, resulting in 30 minutes. The method of combining the boat's speed and river flow to find the net velocity is confirmed as accurate.

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  • Understanding of relative velocity concepts
  • Basic knowledge of speed, distance, and time calculations
  • Familiarity with unit conversions (km/hr to km/min)
  • Ability to apply algebraic equations to solve physics problems
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  • Study relative velocity in fluid dynamics
  • Learn about the effects of current on boat navigation
  • Explore more complex physics problems involving motion in rivers
  • Practice solving problems using the formula time = distance/speed
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Homework Statement


A boat can move at 30 km/hr in still water. how long will it take to move 12 km upstream in a river flowing 6.0 km/hr.

I know the answer is 30 min but the way my teacher explained it is very difficult to remember can someone show me another way to do this problem?

the way she showed us:
Vbg = 30 km/hr
Vbr = Vbg + Vgr = 24 km/hr = 0.4 km/min
Vrg = 6.0 km/hr
Vgr = -6.0 km/hr + 12/0.4 = 30 min
 
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Do you agree that adding the velocity of the boat relative to the water + velocity of the water = velocity of the boat relative to ground (ie: net velocity) ?
 

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