Answer:
A. It is always a positive force
Explanation:
Hooke's law describes the relation between an applied force and extension ability of an elastic material. The law states that provided the elastic limit, e, of a material is not exceeded, the force, F, applied is proportional to the extension, x, provided temperature is constant.
i.e F = - kx
where k is the constant of proportionality, and the minus sign implies that the force is a restoring force.
The applied force can either be compressing or stretching force.
Answer: The correct answers are (A) and (C).
Explanation:
The expression from electrostatic force is as follows;
Here, F is the electrostatic force, k is constant, r is the distance between the charges and 
are the charges.
The electrostatic force follows inverse square law. It is inversely proportional to the square of the distance between the charges. It is directly proportional to the product of the charges.
Like charges repel each other. There is a force of electrostatic repulsion between the like charges. Unlike charges attract each other. There is a force of electrostatic attraction between unlike charges.
The charges are induced on the neutral object when it is placed nearby the charged object without actually touching it.
Therefore, the true statements from the given options are as follows;
Like charges repel.
Unlike charges attract.
Answer:
d. Not enough information is given to answer this question.
Explanation:
From first law of thermodynamics
Q= W + ΔU
Q=Heat ,W= Work , ΔU=Change in internal energy
If work done by the gas :
It means that W and Q both are positive
Q- W = ΔU
Ii Q > W ,then temperature of the gas will increase.
If Q< W ,Then temperature of the gas will decreases.
If work done on the gas:
Q positive but W will be negative
Q- W = ΔU
Q= W or Q>W or Q< W ,then temperature of the gas will increase.
There are three cases because they did not give any information about the work.That is why option d is correct.
Answer:
F(friction) = μ M g definition of frictional force
μ = F / (M g) = 11 N / 50 N = .22
