Answer:
Before giving an injection, a nurse dabs some alcohol onto the patient`s arm. This makes the patient`s skin feels cold. Explain Why ?
<em> Evaporative cooling makes this to be possible</em>
Explanation:
The concept
For a liquid to evaporate, there must be a breakdown of the bond between the molecules of the liquid. These bonds are broken when the molecules gain heat energy. So basically evaporation occurs when the molecules of the substance gain energy in form of heat.
Our Scenario
Just like the way our body excretes sweat on a sunny day, alcohol takes energy from the skin to evaporate. The bond holding the molecules of alcohol breaks faster due to its low boiling point and this account why it evaporates faster. The sudden evaporation of alcohol when dabbed on the skin results in quick utilization of heat energy making the skin feel cold for some time.
The utilization of heat energy from the skin results in evaporation cooling which makes the skin feel colder.
Answer:
B. 4a
Explanation:
Force between the charges is inversely proportional to the square of the distance
=> Force will be 4 times and acceleration will be 4a
=> Answer b).
Answer:
648.40N
Explanation:
Centripetal acceleration is the acceleration of an object around a circular path. Centripetal for e acting on the combined mass is expressed as:
F = ma
F = mv²/r
m is the mass of the object = 143kg
v is the linear velocity = 13.8m/s
r is the radius = 42.0m
Substitute the given parameters into the formula;
F = 143*13.8²/42
F = 27,232.92/42
F = 648.40N
Hence the magnitude of the centripetal force acting on the combined mass is 648.40N
1. Pressure = Force/Area
When a ballon is pressed against many pins then the area is increased as compared to when it is pressed against a single pin. The force by which the balloon is pressed remains the same. Less the area, more the pressure. So, the balloon pops when it is pressed against one pin.
2. The candle goes off when covered with a glass because for burning the candle need oxygen. When glass on placed on the candle then the oxygen supply is stopped. So, when available oxygen is finished, the candle goes off. Water rises in the glass, because when the candle is burning, it expands the air inside the glass due to its heat. But when candle wents off, the air is cooled again and it contracts. So, a vacuum is created. That's why the water rises in the glass to fill the vacuum and to balance the air pressure inside and outside the glass.
3. Objects tend to maintain their state of motion or rest unless subjected to an external force. This property is called Inertia. More the mass more the inertia. When sudden brakes are applied, then our body still tends to remain in motion. That's why our body go forward.
