A-level Mechanics Q3: Need Help w/Calculations

In summary, the conversation discusses question 3 and the confusion with calculations, specifically with adding vectors by components. The solution is provided to add the vectors' x and y components separately and then use trigonometry to find the magnitude and direction of the net force.
  • #1
Shah 72
MHB
274
0
It's question 3. Iam getting a bit confused with the calculations. Pls help
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  • #2
On which part are you stuck? In each case you add the vectors by components.

-Dan
 
  • #3
topsquark said:
On which part are you stuck? In each case you add the vectors by components.

-Dan
Iam getting confused with 30 N.
So f(x) = 40cos alpha - 30 cos alpha
F(y) = 40 sin alpha - 30 sin alpha
 
  • #4
You have three forces, each having x, y, and z components. So:
\(\displaystyle 40 ~ cos( \alpha ) \hat{i} ~ + 40 ~ sin( \alpha ) \hat{j} ~ \text{N}\)

\(\displaystyle 30 \hat{j} ~ \text{N}\)

\(\displaystyle 50 \hat{k} ~ \text{N}\)

Add them and you get F.

-Dan
 
  • #5
the problem statement says the three given forces are coplanar, so you are dealing with x and y components …

$\sum F_x = 0 + 40\cos{\alpha} - 30\sin{\alpha}$

$\sum F_y = 50 - 40\sin{\alpha} - 30\cos{\alpha}$

$|F_{net}| = \sqrt{(\sum F_x)^2+(\sum F_y)^2}$

$\theta = \arctan\left(\dfrac{\sum F_y}{\sum F_x}\right)$
 
  • #6
"Co-planar forces" Hee hee. Sorry for the mistake!

-Dan
 
  • #7
skeeter said:
the problem statement says the three given forces are coplanar, so you are dealing with x and y components …

$\sum F_x = 0 + 40\cos{\alpha} - 30\sin{\alpha}$

$\sum F_y = 50 - 40\sin{\alpha} - 30\cos{\alpha}$

$|F_{net}| = \sqrt{(\sum F_x)^2+(\sum F_y)^2}$

$\theta = \arctan\left(\dfrac{\sum F_y}{\sum F_x}\right)$
Thank you so so much!
 

FAQ: A-level Mechanics Q3: Need Help w/Calculations

1. How do I approach solving A-level Mechanics Q3?

To solve A-level Mechanics Q3, you should first carefully read the question and identify what information is given and what is being asked. Then, you should draw a diagram to visualize the problem and use the relevant equations and principles to solve it.

2. What are the key equations needed to solve A-level Mechanics Q3?

The key equations needed to solve A-level Mechanics Q3 will depend on the specific problem, but some common equations used in mechanics include Newton's laws of motion, the equations of motion, and the laws of conservation of energy and momentum.

3. How do I handle calculations involving vectors in A-level Mechanics Q3?

In A-level Mechanics Q3, you may encounter calculations that involve vectors. To handle these, you should break the vectors into their components and apply the relevant equations to each component. Then, you can combine the components to find the final answer.

4. What are some common mistakes to avoid when solving A-level Mechanics Q3?

Some common mistakes to avoid when solving A-level Mechanics Q3 include using incorrect equations, not considering all forces acting on an object, and not paying attention to the units of measurement. It is important to carefully check your work and make sure it is logically and mathematically correct.

5. How can I practice and improve my skills in solving A-level Mechanics Q3?

To practice and improve your skills in solving A-level Mechanics Q3, you can find additional practice problems online or in textbooks. You can also work with a study group or seek help from a teacher or tutor. Practicing regularly and seeking feedback will help you improve your problem-solving abilities.

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