2 simple Physics q's driving me nuts

• kangta
In summary, the conversation discusses two problems related to rotational equilibrium involving torques and the placement of a pivot support. The first problem involves two children of different weights sitting on a seesaw and determining the placement of the pivot support for equilibrium. The second problem involves a meterstick being balanced with a weight hanging from one end and finding the weight of the meterstick. The solution to both problems involves setting the sum of the torques equal to zero and solving for the unknown variable. The conversation also suggests checking a textbook for more in-depth analysis on rotational motion.
kangta
This looks really simple , but my teacher didn;t explain how to do them so i have no clue how to approach them cna someone kindly help?

1. A 400 N child and a 300 N child sit on either end of a 2.00 m long seesaw. where along the seesaw should the pivot support be placed to ensure rotational equilibrium?

2. A uniform meterstick, supported at the 30.0 cm mark, is balanced when a .50 N weight is hung at the 0 cm mark. What is the weight of the meterstick?

For static equilibrium, the sum of the Torques must equal 0.

Torque is a vector, and is equal to distance X force

so how would i solve these problems?

Like I said: sum the torques. set equal to zero. torque is force times distance.

400*x - 300*(2-x) = 0

There will be a better analysis in your book, I'm sure. Check for the chapter on rotational motion.

Last edited:
as for the second part of your question:

the torques in both direction have to be the same again
torque one arises from .5 N being placed at .3 m from the axis of rotation. the second torque is going to originate from the mass of the meter stick acting at the center of mass of the meter stick( in this case .5 m because the stick has a uniform density)
equate the torques and you have an equation with one unknown. solve for it.

1. What is the difference between speed and velocity?

Speed is a measure of how fast an object is moving, while velocity is a measure of both the speed and direction of an object's motion.

2. How do I calculate acceleration?

Acceleration is calculated by dividing the change in an object's velocity by the time it took for that change to occur. The formula for acceleration is: a = (vf - vi) / t, where a is acceleration, vf is final velocity, vi is initial velocity, and t is time.

3. What is Newton's first law of motion?

Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an unbalanced force.

4. How does friction affect an object's motion?

Friction is a force that opposes the motion of an object. It can cause an object to slow down or come to a stop. The amount of friction depends on the surface the object is moving on and the force pushing against it.

5. What is the difference between potential and kinetic energy?

Potential energy is the energy that an object possesses due to its position or condition, while kinetic energy is the energy an object possesses due to its motion. Potential energy can be converted into kinetic energy and vice versa.

• Introductory Physics Homework Help
Replies
2
Views
8K
• Introductory Physics Homework Help
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
8
Views
8K
• Introductory Physics Homework Help
Replies
1
Views
4K
• Introductory Physics Homework Help
Replies
2
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
3K
• Introductory Physics Homework Help
Replies
4
Views
10K
• Introductory Physics Homework Help
Replies
9
Views
6K
• Other Physics Topics
Replies
1
Views
3K
• Introductory Physics Homework Help
Replies
14
Views
11K