Answer:
Explanation:
When we apply a horizontal force of 76 N to a block, the block moves across the floor at a constant speed. So net force on the block is zero .
It implies that a force ( frictional ) acts on it which is equal to 76 N in opposite direction ( friction )
When we apply a greater force on it it starts moving with acceleration .
This time kinetic friction acts on it due to rough ground equal to 76 N .This is limiting friction ( maximum friction )
Net force on the body in later case
= 89 - 76
= 13 N
Force by ground on the block in horizontal direction = 76 N ( FRICTIONAL FORCE )
=
2/5 = .4
.4*100= 40%
Alex spends more time
Answer:
The statement "The magnetic field of a magnet comes out of the north pole and goes into the south pole" is imprecise
Explanation:
This is because the zero divergence equation (∇ · B = 0 ) is valid for any magnetic field, even if it is time dependent rather than static. Physically, it means that there are no magnetic charges otherwise we would have ∇ · B ∝ ρmag instead of ∇ · B = 0. Consequently, the magnetic field lines never begin or end anywhere in space; instead they form closed loops or run from infinity to infinity.
Answer: A. Work is done on the system and heat is transferred from the system for a net decrease in internal energy.
Explanation:
A refrigerator is a device which dispenses heat from the close system to a warmer area or in the surrounding. By dispensing the heat the internal temperature of the refrigerator drops. The system of refrigerator violates the second law of thermodynamics. As it performs the work to cool the region instead of heating the region. The work is done on the system and the internal energy decreases and the heat energy is liberated to the surrounding area. A refrigerator is an open system.
The correct answer is B. Calcite
Explanation:
Mohs hardness scale indicates the hardness of minerals using a scale from 1 to 10 as well as defining the objects or tools that can be used to scratch the minerals. These two features of minerals are shown in the table of the image. About this, it is shown gypsum and talc can be scratched by just a fingernail, considering minerals with a hardness of 2.5 or below can be scratched by a fingernail. In the case of calcite that has a hardness of 3, this cannot be scratched by a fingernail, but it can be scratched by a penny, which works for minerals with a hardness of 3.5 or below. Thus, the correct answer is Calcite.
