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Because metals expands when its temperature increases and according to the question the metal lid will also expand when t is put in hot water and the bottel can be oppened easily

When a bottle with a tightly-closed metal lid is put in hot water for sometime, its lid can be opened easily because metals have greater coefficient of expansion than glass. Therefore, when the metal lid comes in contact with hot water, it'll expand more than the glass container. As a result, it will be easier to open the bottle.

An ordinary electric fan does not cool the air, it gives comfort in summer because it circulates the air only present in the room.due to this, evaporation takes place and we feel cool

When a bottle with a tightly-closed metal lid is put in hot water for sometime, its lid can be opened easily because metals have greater coefficient of expansion than glass. Therefore, when the metal lid comes in contact with hot water, it'll expand more than the glass container. As a result, it will be easier to open the bottle.
No, the angular momentum of a body about a point can be expressed as mvr. Since it depends on 'r', it will be different about different points.
Yes, The moment of inertia is always less for an axis passing through the center of mass than any other parallel axis.  From the parallel axis theorem I1 = ICom + md² where d is the distance between the parallel axes. Hence ICom < I1.
Yes, if all the particles of a system lie in the X-Y plane, then it's necessary that its centre of mass lies in the X-Y plane. As we know,  As all the particles lie in the X-Y plane, their z -coordinates are zero. Therefore, for the whole system, zcm=0 ; i.e., its centre of mass lies in the X-Y plane.
Substitute x=1 to test this function. In numerator, the angle is x−1 and it can be obtained in denominator as well by expressing x2−1 as two multiplying factors in which x−1 is one of them. Therefore, the value of first multiplying factor is 1 and substitute x=1 in the second multiplying factor to obtain the required solution.  
The centre of mass of a body can lie within or outside the body. For example, centre of mass of a uniform rod lies at its geometrical centre which lies within the rod whereas centre of mass of a uniform ring lies at its geometrical centre which lies outside the ring.
On drying, the weight of water changes but the ratio of silica with other materials remains constant. If x is the % of silica in the original sample, (88−x) is the weight of the materials other than water and silica.
Work done to bring q1 from infinity to r1 = q1v(r1) Work done to bring q2 from infinity to r2 = q2v(r2) Also, work done on q2 to move it against the field due to Where, distance between q1 and q2 . . potential energy of the system
1st law = the velocity of a body remains constant unless the body is acted upon by an external force. eg - a book kept in the table remains there forever unless an external force acts upon it. 2nd law = rate of change of momentum is directly proportional to external unbalanced force and the change in momentum takes place in the same direction of force. eg - If you use the same force to push a...
Gauss's law for the electric field describes the static electric field generated by a distribution of electric charges. It states that the electric flux through any closed surface is proportional to the total electric charge enclosed by this surface.
The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction.
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