Calculating Reactions in Balance: A Student's Question

• clockworkrobot
In summary, the person is an architecture student trying to calculate reactions in a given problem. They have attempted the question and received two values, but are unsure how to determine whether the reaction is clockwise or anticlockwise. They are seeking clarification on how to do this and whether their answers are correct.

clockworkrobot

Hi all,

I am an architect student in college and I am trying to calculate the reactions in the question in the follwing url ( https://www.flickr.com/photos/123626386@N07/16250310830/ ) I have attempted the question and got two values which can be seen in the following url (https://www.flickr.com/photos/123626386@N07/16251461949/ ) . What I don't understand though is how to calculate whether the reaction is clockwise or anticlockwise thus assigning it a positive or negative value if anyone could tell how to do this and whether my answers are correct it would be greatly appreciated!

Many thanks,
Clockworkrobot

clockworkrobot said:
Hi all,

I am an architect student in college and I am trying to calculate the reactions in the question in the follwing url ( https://www.flickr.com/photos/123626386@N07/16250310830/ ) I have attempted the question and got two values which can be seen in the following url (https://www.flickr.com/photos/123626386@N07/16251461949/ ) . What I don't understand though is how to calculate whether the reaction is clockwise or anticlockwise thus assigning it a positive or negative value if anyone could tell how to do this and whether my answers are correct it would be greatly appreciated!

Many thanks,
Clockworkrobot
The reactions are forces, not torques, so there is no question of clockwise or anticlockwise for those.
To deduce them, you wrote a torque equation. In the way you've written it, you've taken the reactions as positive upwards, but the loads as positive downwards. That required you to reverse the signs.
A purist might have written the equation so that all forces are positive upwards and all torques positive anticlockwise, giving
RL*0 + (-25)*0.4 + (-10)*0.6 + RR*1.2 = 0.

1. How do I calculate reactions in balance?

To calculate reactions in balance, you need to first identify the reactants and products in the chemical equation. Then, use the law of conservation of mass to determine the quantity of each element present on both sides of the equation. Finally, use simple algebraic equations to balance the number of atoms on each side of the equation.

2. What is the purpose of balancing reactions?

The purpose of balancing reactions is to accurately represent the chemical changes that occur in a chemical reaction. Balancing ensures that the same number of atoms of each element is present on both sides of the equation, which follows the law of conservation of mass.

3. What are the key concepts to understand when balancing reactions?

The key concepts to understand when balancing reactions include the law of conservation of mass, the concept of moles and molar ratios, and the use of coefficients to balance equations. It is also important to understand the types of reactions, such as synthesis, decomposition, single replacement, and double replacement.

4. How can I check if a reaction is balanced?

To check if a reaction is balanced, you can count the number of atoms of each element present on both sides of the equation. Another way is to calculate the mass of each element on both sides of the equation and ensure that they are equal. Additionally, you can use an online balancing tool or ask a teacher or tutor to check your work.

5. What are some common mistakes to avoid when balancing reactions?

Some common mistakes to avoid when balancing reactions include forgetting to include coefficients, forgetting to balance polyatomic ions, and incorrectly identifying the reactants and products. It is also important to make sure that the final balanced equation has the lowest possible whole number coefficients.