Work 2 - Angles


Sometimes, the force is applied at an angle, but the object actually moves horizontally.

Question 1
Study this diagram which shows a force F = 20N being applied at an angle of 600 to a box as shown. The box is thus moved 5m rightwards.

Diagram 1
1.1. Calculate the WORK done by the 20N force at the 600 angle.
The work done is ZERO since the box is not moving in the 600 direction . For work to be done by a force, the object MUST move in the direction of THAT force.

1.2. Calculate the WORK done by the 20N force horizontally, i.e. for the 5m distance.
Since the actual applied force is at an angle, we have to resolve it into it's components Fx and Fy. We have to do this to find the horizontal force because the box is moving horizontally.
So draw the triangle, and apply trig.


Diagram 2


Now we know the actual size of the force in the horizontal direction.

Therefore the work done is:


1.3. How much of work is done by Fy?
Zero.
There is no movement in the vertical direction.



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