After researching the possible effects of music, elaina proposes that if people listen to faster-paced music, their pulse rates will increase more than if they listen to slower music. her mother listens to classic rock at a high volume for 30 minutes, her younger brother listens to classical music quietly while he sleeps at night, and her grandmother listens to two hours of rap at a medium volume. elaina records each person's pulse before and after listening to the music. what is missing from elaina's scientific investigation?

Elaina's scientific investigation is missing controlled variables.

Explanation:

A good scientific investigation should vary only the factor that is studied (the speed of the music. All other factors should be kept constant.

She hasn’t controlled for volume. The volume of the music may affect the rate at which the listener’s heart rate will increase. She should have measured each person’s pulse after the same period of listening.

She hasn’t controlled for age. A grandmother may respond to loud music differently from a teenager. All her subjects should be about the same age.

She hasn’t controlled for wakefulness. A person may respond to music differently when awake than when asleep.

controled variables

Explanation:

i took the test

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.

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.