9th Class Physics Notes “Analogue Stop Watch”
Construction of Analogue stop watch:
Analogue stop consist of two hand minute hand, second hand and knob which used for ‘start and stop stop watch.
Working of analogue stop watch:
Analogue stop watch has a knob that is used to start, stop and reset the stop watch by pressing and releasing it. The stop watch start when the knob is pressed once. When the second hand complete one rotation of 60 second, the minute hand advance by one division.
When we want to stop the stop watch the knob is pressed second time and the third press brings the needle of stop watch to zero position.
Q: How a measuring cylinder is used to find out the volume of an object.
Measuring cylinder:
Definition:
A device which is used to measure the volume of liquid and also used to measure the volume of irregular solid body is called measuring cylinder.
Construction:
Measuring cylinder is made of transparent glass or plastic. It has a vertical scale which is graduated in millimeter or cubic centimeter.
Working:
Take a measuring cylinder; place it vertically on the flat surface. Now pour some water in the cylinder, the volume of water is read from the scale on the side. The surface of the liquid curve upward at the point where it touches the inside of the cylinder. This curvature is called meniscus.
Correct method to note the level of a liquid:
The correct method to note the level of liquid in the cylinder is to keep the eye at the same level as the meniscus of the liquid. It is incorrect to not the liquid level keeping the eye above or below the level of liquid.
Q: Define and explain the significant figure, write the rule of significant figure.
Significant figure:
Definition:
in any measurement the combination of accurate known digits and first doubtful digit is called significant figure.