Center of mass question (man on a boat)

Click For Summary
SUMMARY

The discussion revolves around calculating the new center of mass (CM) of a system consisting of a man and a boat. The man, with a mass of 60 kg, initially stands at the left end of a uniform boat weighing 169 kg and measuring 2.7 m in length. The center of mass equation used is X=(m1x1+m2x2)/(m1+m2). After the man walks to the right edge of the boat, the calculated new position of the center of mass is 0.65 m, but this result is disputed as incorrect by SmartPhysics, prompting further inquiry into the interpretation of the problem's absolute position.

PREREQUISITES
  • Understanding of center of mass calculations
  • Familiarity with the concept of reference points in physics
  • Knowledge of mass distribution in a system
  • Basic algebra for solving equations
NEXT STEPS
  • Review the principles of center of mass in physics
  • Study the implications of reference points in motion problems
  • Examine examples of similar problems involving moving masses
  • Explore potential errors in physics simulation tools like SmartPhysics
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and center of mass concepts, as well as educators seeking to clarify common misconceptions in these topics.

ddtozone
Messages
8
Reaction score
0

Homework Statement



A man with mass m1 = 60 kg stands at the left end of a uniform boat with mass m2 = 169 kg and a length L = 2.7 m. Positive x is pointing to the right. Assume there is no friction or drag between the boat and water. After the man walks to the right edge of the boat, what is the new location the center of the boat?
(The boat lies on the x-axis, so they're looking for the absolute position of the center.

Homework Equations



X=(m1x1+m2x2)/(m1+m2)
The absolute location of the CM will not change.

The Attempt at a Solution


First the CM equation (169*1.35)/(169+60) gives me x = 1 (relative to the boat) as the position of the center of mass, which I use as a reference point for the x-axis.
When the man moves to the right, I plug in (60*2.7+169*1.35)/(169+60) and I get x = 1.7 relative to the boat. Since the center has moved to the left, I do 1.7 - 1 = 0.7 to find the distance the center has gone. Finally I subtract that change in distance from the original position with 1.35 - 0.7 = 0.65. But SmartPhysics says this is wrong. Does someone have any further insight here? Thank you!
 
Physics news on Phys.org
ddtozone said:
A man with mass m1 = 60 kg stands at the left end of a uniform boat with mass m2 = 169 kg and a length L = 2.7 m. Positive x is pointing to the right. Assume there is no friction or drag between the boat and water. After the man walks to the right edge of the boat, what is the new location the center of the boat?
(The boat lies on the x-axis, so they're looking for the absolute position of the center.

The question doesn't provide an origin against which positions are to be measured, so how is 'absolute position' to be interpreted? Is this the precise and complete wording of the problem?
 
gneill said:
The question doesn't provide an origin against which positions are to be measured, so how is 'absolute position' to be interpreted? Is this the precise and complete wording of the problem?

because this is a question with multiple parts, and the answers to the first parts are based on the reference points of the boat's initial position, with the left of the boat starting at x=0. I guess there's a chance that SmartPhysics has an error, but I'm completely stumped.
 
Last edited:

Similar threads

  • · Replies 7 ·
Replies
7
Views
7K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 1 ·
Replies
1
Views
8K
  • · Replies 25 ·
Replies
25
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 6 ·
Replies
6
Views
4K