Answer:
20 J
Explanation:
Given:
Weight of the book is, 
Height or displacement of the book is, 
The work done on the book to raise it to a height of 2 m on a shelf is against gravity. The gravitational force acting on the book is equal to its weight. Now, in order to raise it, an equal amount of force must be applied in the opposite direction.
So, the force applied by me should be equal to weight of the body and in the upward direction. The displacement is also in the upward direction.
Now, work done by the applied force is equal to the product of force applied and displacement of book in the direction of the applied force.
Therefore, work done is given as:
Therefore, the work done to raise a book to a height 2 m from the floor is 20 J.
The correct answer to your question here is D
Yes, our friend is right, because there is no contradiction to the law of conservation of mass in the above equation. It just the mass of the product is equal to the mass of reactants.. and that is shown in the equation you have presented earlier
Answer: The property that will best provide evidence that the samples are solid includes:
--> if the substance has a definite shape,
-->if the substance has a definite volume
--> if it's tightly packed.
Explanation:
According to the kinetic theory of matter, every substance consist of very large number of very small particles called molecules. These molecules, which are made up of atoms that are the smallest particles of a substance that can exist in a free state.
Matter can exist in the following states:
--> Solid state
--> liquid state or
--> Gaseous state.
The general property of a substance that is in gaseous state includes:
--> Definite shape: A substance can be grouped as a solid if it's shape is fixed that is, it doesn't depend on the shape of other materials.
--> Definite volume: A substance can be grouped as a solid if it occupies its own shape. This is due to the force of cohesion among its molecules.
--> Tightly packed: A substance can be grouped as solid if the molecular movements of the particles are negligible.
From the samples under observation by Juan and kym, if the sample that possesses the above described qualities, it is a solid rather than liquid or gas.
