The image shows a tennis ball hitting a tennis racket. According to Newton's third law of motion, which of the following best describes the forces of the tennis racket and the ball? A. The tennis racquet applies a greater force on the ball than the ball applies on the racket. B. Both the tennis racket and the ball experience equal forces in the same direction. C. Both the tennis racket and the ball experience equal forces but in opposite directions. D. Neither the tennis racket nor the ball experiences the force of gravity.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.