What distance does the boat move

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In summary, the question asks for the distance the boat moves when a boy with a mass of 36kg moves from the stern to the bow of a boat with a mass of 80kg and a length of 2.8m, assuming water resistance can be neglected and the center of mass remains at rest. The center of mass formula is used to show that the change in the center of mass for the boat and boy is equal to 0, regardless of the location of the center of mass. Additionally, there are suggestions for finding A level notes on various topics.
  • #1
misstoi21
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The mass of a boat is M=80kg, the mass of a boy is m=36kg. The boy moves from the stern to the bows of the boat. What distance does the boat move, if its length is 2.8m? At such low speeds the water resistance may be neglected. Hint: Center of mass remains at rest.

Please help me because I am stumped :confused:
 
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  • #2
misstoi21 said:
Hint: Center of mass remains at rest.
This question is best suited for the Homework help section.

Why not try your own hint? Calculate the center of mass (with respect to the boat) of the boat&boy in these two cases:
(1) Boy at stern
(2) Boy at bow

What must have happened?
 
  • #3
Hasn't there been a question just like this at least twice in the past week or so?

cookiemonster
 
  • #4
I thought so too, cookiemonster. See if you can find it.
 
  • #5
Well, I can't find them, so here we go again.

Do you have an equation to find the center of mass of two objects, misstoi21? What is it? What would it be for when the boy is at the stern and what would it be for when the boy is at the bow? Don't these two have to be equal?

Also, please don't make a new thread in order to post a reply. Please use the "Post Reply" button at the bottom of the page.

cookiemonster
 
  • #6
The formula for centre of mass is something like this



d, d1, and d1 are all relative to a given point. I think you have to assume that the centre of mass for the boat is in half-way between the front and back of the boat.

On second thought it could just be an inertia thing like this



I'll work on this a bit more.
 
Last edited:
  • #7
Ok instead of trying to figure out some formula then get a value then plug it into another formula, just make 1 giant formula.

d does not change



So then switch that around once



Sub it in once







Since the denominator will never affect whether it is zero or not, it can just be cut out of the equation.



That's the same equation I had above which shows that inertia is conserved. How awesome is that? :smile:
 
  • #8
Actually, the location of the center of mass of the boat is irrelevant. Its change will be the same regardless of where it is.

cookiemonster
 
  • #9
can anybody send or give me the address of a good site where I can find some good A level notes?about any topic.

Thank you
 
  • #10

FAQ: What distance does the boat move

How is the distance that a boat moves calculated?

The distance that a boat moves is calculated by multiplying the speed of the boat by the time it has been moving. This gives the total distance traveled by the boat.

Does the distance that a boat moves depend on the water conditions?

Yes, the distance that a boat moves can be affected by the water conditions such as currents, tides, and wind. These factors can either increase or decrease the distance traveled by the boat.

How does the weight of the boat affect the distance it moves?

The weight of the boat can affect the distance it moves as it can impact the boat's speed and maneuverability. A heavier boat may require more power to move and may not be able to reach high speeds, resulting in a shorter distance traveled.

Is the distance a boat moves affected by the boat's shape?

Yes, the shape of a boat can affect the distance it moves. A boat with a streamlined and aerodynamic shape will experience less drag in the water, allowing it to move faster and cover a greater distance compared to a boat with a less streamlined shape.

Can the distance a boat moves be affected by the type of propulsion used?

Yes, the type of propulsion used can impact the distance a boat moves. For example, a boat with a motor will be able to cover a longer distance compared to a boat powered by oars or sails, as it can achieve higher speeds and maintain them for longer periods of time.

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