VECTORS AND FORCES

I. BASIC IDEAS
Forces are involved in everything that happens around us. We use force to move things around. Even standing still involves forces.

For Cases 1 - 5, the movement is linear. That means all the forces lie along one line, even if they are in different directions. (Place your mouse cursor over the black arrows to see an illustration). Each black arrow represents a force in the direction it points to. The gray arrows show what happens next, and the dotted gray lines represent movement.

1.

If a box was pulled gently to the right, it would move to the right slowly
2.

If pulled hard to the right, it would move to the right quickly
3.

Now, if the box is pulled hard to the right and gently to the left... it would move to the right. However, some of the rightward force has been cancelled out, so the box moves slowly as in Case 1.

In Cases 1 - 3, you can work out magnitude of the resultant forces (the 'combined' forces) (daya paduan) by adding the forces together. Usually, right and up are positive directions, whereas left and down are negative directions (although this might not always be the case). In Cases 1 and 2, there is only 1 force involved so no calculation is needed.

For Case 3, let each black arrow be the force of 1 Newton:

= 2 + (-1)        <- The right (positive) force plus the left (negative) force
= 2 - 1
= 1 N

The final direction is positive, so it's to the right.
4. If a box is being pulled gently in opposite directions, it stays still. This is because the resultant force is nought (Daya paduan sifar), as if no forces are at work.
= 1 + (-1)
= 0 N

The box is said to be "experiencing forces which are in equilibrium" ("mengalami keseimbangan daya")

5. If pulled hard in opposite directions, it still stays still. Compare with Cases 3 and 4.
= 2 + (-2)
= 0 N

 
6.

 

If the box is pulled to the right and upwards, the box would move diagonally.

Here, the movement is no longer linear. There are two lines involved: Left-right and up-down (Again, move your cursor over the diagram below). Therefore, you CANNOT simply add the forces like above. Also note that the final direction DOES NOT follow either one of the two forces (i.e. the resultant force is in a totally different direction)

Page: 1 | 2 | 3
The Notes Portal Home

 

1