P5 - Calculating Forces Flashcards
What do scale drawings help you with?
They can help you resolve forces or work out the resultant force
How do you draw a scale drawing to find the resultant force?
1) Draw all the forces acting on an object,to scale
2) Then draw a straight line from the start of the first force to the end of the last force - this is the resultant force
3) Measure the length of the resultant force on the diagram to find the magnitude and the angle to find the direction of the force
A man is on an electric bicycle that has a driving force of 4N north.However, the wind produces a force of 3N east.Find the magnitude and direction of the resultant force
1) Draw the scale drawing of the forces acting
2) Make sure you choose a sensible scale (e.g 1cm = 1N)
3) Draw the resultant force from the tail of the first arrow to the tip of the last arrow
4) Measure the length of the resultant with a ruler and use the scale to find the force in N
5) Use the protractor to measure the direction as a bearing
(The resultant force in 5N on a bearing of 037 degrees)
What does it mean if an object is in equilibrium?
All the forces acting on an object combine to give a resultant force of zero
(NOTE : On a scale diagram,this means that the tip of the last force you draw should end where the tail of the first force you drew begins.For example for three forces,the scale diagram will form a triangle)
How do you find a missing force if the object is in equilibrium?
Draw out the forces you do know and told(to scale and tip-to-tail).Then join the end of the last force to the start of the first force.The line is the missing force so you can measure its size and direction.
Do all forces act horizontally and vertically?
No,some forces act at awkward angles
How can you make forces at awkward angles easier to deal with?
Split the forces into two components at right angles to each other(usually horizontal and vertical),acting together these components have the same affect as the single force.You can resolve the force(split it into componenets) by drawing it on a scale grid.Draw the force to scale,and then add the horizontal and vertical componenets along the grid lines.Then you can just measure them.
