Answer:
1.The calorie was originally defined as the amount of heat required at a pressure of 1 standard atmosphere to raise the temperature of 1 gram of water 1° Celsius. Since 1925 this calorie has been defined in terms of the joule, the definition since 1948 being that one calorie is equal to approximately 4.2 joules.
2.Boiling water at 100 degrees Celsius: 540 calories are needed to turn 1 gram (at 100 degrees Celsius) of water to steam.
The pressure at the depth h in the ocean is given by (Stevin's law)

where

is the atmospheric pressure
and

is the pressure exerted by the column of water of height h=4267 m, with

being the water density and

.
Substituting, we find

We want to convert this into atmospheres: we know that 1 atm corresponds to the atmospheric pressure at sea level, so

, therefore we just need to divide by this number:
The electric field generated by a point charge is given by:

where

is the Coulomb's constant
Q is the charge
r is the distance from the charge
We want to know the net electric field at the midpoint between the two charges, so at a distance of r=5.0 cm=0.05 m from each of them.
Let's calculate first the electric field generated by the positive charge at that point:

where the positive sign means its direction is away from the charge.
while the electric field generated by the negative charge is:

where the negative sign means its direction is toward the charge.
If we assume that the positive charge is on the left and the negative charge is on the right, we see that E1 is directed to the right, and E2 is directed to the right as well. This means that the net electric field at the midpoint between the two charges is just the sum of the two fields:
Answer:
Keeping the speed fixed and decreasing the radius by a factor of 4
Explanation:
A ball is whirled on the end of a string in a horizontal circle of radius R at constant speed v. The centripetal acceleration is given by :

We need to find how the "centripetal acceleration of the ball can be increased by a factor of 4"
It can be done by keeping the speed fixed and decreasing the radius by a factor of 4 such that,
R' = R/4
New centripetal acceleration will be,




So, the centripetal acceleration of the ball can be increased by a factor of 4.
Answer:
False
Explanation:
This proposition is false because by example the sun exerts a force over the earth and them are not in contact