How to Calculate MA of Pulleys

How to Calculate MA of Simple Machine of Pulleys

The effort needed to lift a load can be halved by using two pulleys: one fixed and the other moving. A single rope is passed over these pulleys. One end of which is fixed while the other end is attached to the effort. If the pulleys are frictionless, the tension in the rope remains the same in its entire length.

As seen from the (free body diagrams), the effort (E) is equal to the tension (T) in the rope. Tension in two rope segments balances the load (W).
Hence,
E = T and W = 2T

Mechanical Advantage (MA) is the ratio of load overcome to effort applied. In this case,
MA = W/E = 2T/T = 2

Play this movie to know well about Mechanical Advantage of pulley:

By looping more ropes around more pulleys we can continue to increase the mechanical advantage.
Learn this image!

Experiment of Centrifugal Force

Centrifugal force is the fictitious effect that appear when an object is doing a circular motion. Centrifugal means moving away from the center of rotation. For example, every time we are in a car and take a bend - we feel a force pushing us to the outside of the curve. Or, If you ever go to dunia fantasi in Jakarta and ride rotation train (rollercoaster), when the train rotates and turned up, why don’t you fall? That is the effect of centrifugal force. Same as that event, in this activity you will show that water in a pail, when the pail rotates, the water does not spill, although when the pail is above, the pail faces downward turned up.

What do you need?

• A string of length 60 cm.
• A small plastic pail.
• 250 ml water.

What must you do?

Comparison of Alcohol and Mercury Thermometer

The word thermometer comes from the word thermos meaning warm and meter meaning measuring device. Etymologically, the thermometer is a device used to measure the temperature appropiate and express it by a number.
Thermometer is commonly made of a glass tube which is filled with liquids. The liquids are used as a thermometer filler, because the liquids undergo the change in volume if the temperature changes.

Commonly, thermometers use alcohol and mercury to fill their tubes, because alcohol and mercury have superiorities compared with anothers. However, there are also the weaknesses of alcohol and mercury. Meanwhile, if we compare between mercury and alcohol thermometer, we will find the superiorities and weaknesses of alcohol and mercury. Those are as follows:

Measuring Temperature by Using Touch-Sensory Organ

In everyday life, we often hear or even feel hotness and coldness. Usually, to feel the hotness or coldness of a body, we only use the sense by touch-sensory organ. For example, the ice cream feels cold when we hold it, the boiling water feels hot when we touch it, or at noon the air feels hot. However, basically, the touch-sensory organ of everyone in feeling something, mainly about the hotness or coldness of a body are relatively different. Hence, measuring hotness and coldness degree of a body by using touch-sensory organ is not always correct and relative, it depends on the tendency of the sense and the sensitivity of the touch-sensory organ for everyone.

The hotness or coldness degree of a body is called temperature. In the discussion above it has been explained that to measure the temperature, you cannot use touch-sensory organ, because the result is relative. To prove it, do the following activity: