Elena held a rock weighing 1 N in her hand. The rock has no velocity.
KE?

KE = 0

Energy is the ability to do work  

Energy because its motion is expressed as Kinetic energy (KE) which can be formulated as:  

So for two objects that have the same speed, the greater the mass of the object, the greater the kinetic energy  

The stone in hand is in a motionless state (at rest) so that its velocity (v) = 0, so it has no kinetic energy

But this stone can have potential energy that is gained due to its height

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.