Mechanics - Forces and Motion
Pearson Edexcel Mathematics 2022
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Flashcards
Force diagrams and equilibrium
What is a force diagram?
A diagram showing all the forces acting on an object.
What should you draw whenever you have a problem involving forces in Mechanics?
A force diagram.
In $\hat{i}$ and $\hat{j}$ notation, what is the value of a resultant force for an object in equilibrium?
Parallel vectors and solving for unknowns
If
\[ \left(\begin{matrix} 2+p \\ 5+q \end{matrix}\right) \]
is parallel to
\[ \left(\begin{matrix} 1 \\ -2 \end{matrix}\right) \]
, what equation could you write in terms of a new variable $k$ to aid in solving?
If
\[ \left(\begin{matrix} 2+p \\ 5+q \end{matrix}\right) = \left(\begin{matrix} 1k \\ -2k \end{matrix}\right)\]
is true, what two equations can you write?
\[2+p = k \\ 5+q = -2k\]
How could you rewrite this so it’s just in terms of $p$ and $q$?
Ladder and hinge questions
What’s the normal procedure for answering a ladder or hinge question?
- Take moments
- Resolve forces
How many components of reaction are there at a wall in a ladder question?
Reactions, friction and reading questions
Why is the reaction on a smooth surface always perpendicular to the surface?
As the surface is smooth, there is no friction and so the reaction is unchanged.
When reading a tricky mechanics question, what is it a good idea to do?
Circle all words like “smooth”, “rough”, “uniform”, etc.
Is the reaction force necessarily the resultant force?
No, not if there is friction involved.
Pulleys and strings
If a string connecting two particles over a pulley is not actually light, what will be true?
The tensions will no longer be equal.