Download Simple Machine Practice Problems

Simple Machine Practice Problems
1. Using a ramp of length 2m, I apply a 150N force to move a 20kg
object a vertical distance of 1m.
i) How much work do I do on the object?
+300J
ii) How much work does gravity do on the object?
-200J
iii) What is the efficiency of my machine?
67%
iv) How much of my input force is used to counteract friction on the
ramp?
50N
2. I’m using a pulley system with an ideal mechanical advantage of 4.
i) If I want to raise a 10kg object up at constant velocity, what input
force is required?
25N
ii) If I want to raise the object 20cm, over what distance should I
apply the input force?
80cm
iii) If the actual input force required is 30N, what is the mechanical
advantage of my system?
3.3
iv) What is its efficiency?
83%
3. Mechanical Advantage and Machine efficiencies are both ratios.
However, one of them can never be greater than one while the
other one is always greater than one. Explain why.
Output work is never greater than input work (you always do extra work
to counteract frictional effects), so efficiency is never greater than one
In a machine, the output force is usually greater than the input force
(otherwise, why would you use the machine?), so MA is usually greater
than 1