Answer:


Explanation:
Force of friction on M mass so that it will move down the inclined plane is given as

now if it is moving down the inclined plane at constant speed
so we will have

on other side the mass "m" will go up at constant speed
so we have

so we have

so we have

for special case when m = M
then we have

Answer:1). Distance of far point x=0.9m
Therefore, since the image is virtual
-f=-x = -0.9m
Power of the concave lenses = 1/f = 1/-0.9
= -1.11D
2 ) near point is 21cm = 0.21m
Power = 4-1/near point
= 4/0.21
= 14.2D.
Answer:
yes it is essential
Explanation:
a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit; controls current flow into a circuit
Answer:
false gravity is not considered matter
Explanation:
Nuclear reactions are the reactions in which nucleus of an atom changes either by splitting or joining with the nucleus of another atom.
There are two types of nuclear reactions.
- Nuclear fission - In this process, large atomic nuclei splits into smaller nuclei.
- Nuclear fusion - In this process, two small nuclei combine together to form a large nuclei.
Both nuclear fission and fusion processes involve nuclei of atoms.
For example, 
Thus, we can conclude that statements which are true are as follows.
- Nuclear reactions involve the nuclei of atoms.
- The products of nuclear reactions are lighter than the reactants.