What Is the Speed of the Man Relative to the Ground?

In summary, the man's speed relative to the ground is 20 km/hr. This is calculated by adding the boat's speed relative to the river (14 km/hr) to the man's speed relative to the river (6 km/hr). The difference in speeds between the boat and the river (8 km/hr) is not relevant to the man's speed relative to the ground.
  • #1
Captain Levi
6
0

Homework Statement


If a river is going 6 km/hr relative to the ground, a boat is going 14 km/hr relative to the river, and a man is jumping from one end of the boat to the other at 6 km/hr relative to the river. What is the speed of the man relative to the ground?

I'm stuck between the answers: 14 km/hr and 26 km/hr.

They are all moving in the same direction

Homework Equations


None that I'm aware of

The Attempt at a Solution


Well if you subtract:
River - Ground=6 km/hr
Boat - River= 8 km/hr
Man - River= 0 km/hr so, it equals 14 km/hr
I got 26 km/hr by just adding them together[/B]
 
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  • #2
It says the man is jumping at 6km/h relative to the _river_ is that correct?
 
  • #3
CWatters said:
It says the man is jumping at 6km/h relative to the _river_ is that correct?
Yes.
 
  • #4
Captain Levi said:
boat is going 14 km/hr relative to the river
From that, how do you get:
Captain Levi said:
Boat - River= 8 km/hr
?

From this:
Captain Levi said:
man is jumping from one end of the boat to the other at 6 km/hr relative to the river.
how do you get:
Captain Levi said:
Man - River= 0 km/hr
?
 
  • #5
From this video that shows examples of similar problems:
 
  • #6
Captain Levi said:
From this video that shows examples of similar problems:

I don't know what part of that you have misunderstood.
Just try using commonsense. If a boat is moving at 14km/h relative to the river, what is the difference in their speeds as measured relative to the bank?
 
  • #7
Well the ground doesn't move correct? So the river moves 6 km/hr relative to the ground. Since the river is moving 6 km/hr and the boat is moving 14km/hr relative to the river, then you subtract their speeds and so from the perspective of the river the boat is moving 8km/hr.

Honestly I'm just following what my teacher told us and it was something like what I explained in the previous paragraph.
 
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  • #8
I asked my question above for a reason but you missed it.

If the man moves at 6km/h relative to the river do you even need to know the velocity of the boat?
 
  • #9
Captain Levi said:
a boat is going 14 km/hr relative to the river
Captain Levi said:
the boat is moving 14km/hr
Spot the difference.
 
  • #10
haruspex said:
Spot the difference.
Sorry the correct one is the boat is going 14km/hr relative to the river. Edited it.
 
  • #11
Captain Levi said:
the boat is moving 14km/hr relative to the river

Captain Levi said:
so from the perspective of the river the boat is moving 8km/hr.

"Relative to the river" and "from the perspective of the river" are the same thing, so how come the speeds are different?
 
  • #12
Captain Levi said:
Well the ground doesn't move correct? So the river moves 6 km/hr relative to the ground. Since the river is moving 6 km/hr and the boat is moving 14km/hr relative to the river, then you subtract their speeds and so from the perspective of the river the boat is moving 8km/hr

Think intuitively rather than following a rigid process. ...

If you were in a plane going 100mph relative to the ground and you walk from the back to the front at 10mph relative to the plane, how fast are you going relative to the ground?

If you are walking forwards would you be going faster or slower than the plane?
 
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FAQ: What Is the Speed of the Man Relative to the Ground?

1. What is relative motion?

Relative motion refers to the movement of an object in relation to another object. It describes the change in position or orientation of an object with respect to a reference point or frame of reference.

2. How is relative motion different from absolute motion?

Absolute motion refers to the movement of an object in relation to a fixed point or frame of reference, such as the Earth. Relative motion, on the other hand, is observed from the perspective of one moving object in relation to another.

3. What factors affect relative motion?

The relative motion of two objects is affected by their individual velocities and directions of motion. Other factors, such as gravity and external forces, can also influence the relative motion between objects.

4. How do you calculate relative motion?

To calculate relative motion, you need to know the velocities and directions of motion for the two objects involved. You can then use vector addition to determine the relative velocity, which is the combined motion of the two objects.

5. What are some real-life applications of relative motion?

Relative motion is used in many fields, including physics, engineering, and navigation. Some examples of its applications include calculating the relative velocities of objects in motion, analyzing collisions, and predicting the positions of celestial bodies.

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