The mass of the water is 14.9 g
Explanation:
When a certain amount of a susbtance is heated, the temperature of the substance increases according to the equation

where
Q is the amount of energy supplied to the substance
m is the mass of the substance
is its specific heat capacity
is the change in temperature
In this problem, we have:
Q = 2500 J of energy supplied to the water
is the specific heat capacity of water
is the change in temperature of the water
Therefore we can solve for m to find the mass of the water:

Learn more about specific heat capacity:
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In case of an object sitting at rest on another base, there are two equal and opposite forces – Normal force and the gravity.
Answer: Option A
<u>Explanation:
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When an object is placed at rest position on another object, there is a force exerted by the surfaces of the two contact objects. This force is denoted as Normal Force.
When an object such as a box is placed on a shelf, its surface exerts a contact force on the base of the shelf- The Normal force directed upward. Meanwhile, the gravity stays at its action and tries to pull the box towards itself.
Both of these forces however are equal and opposite and therefore, there is zero net force on the box. That's why it remains at rest, holding on Newton's third law.