One science physics question for the second year of junior high school, and one science question for

Answer: C Analysis: A. "The glass will not break if it is thrown against the wall" is not certain.

Fixed, because the glass is damaged when it hits the wall, is caused by the impact.

The force of the blow is determined and has nothing to do with gravity.

b. Mass is a property of the physical substance itself. And gravity.

It is the result, and quality is only one of the factors that produce this result.

Cause. That is, mass is a necessary but not sufficient condition for the generation of gravity.

By the absence of gravity, it is not possible to conclude that there is no mass.

c. Without the restraint of gravity, the matter is in a suspended state.

Even the slightest elasticity can make you float off the ground when jumping.

Ball. d. The force of grasping hair is the internal function of the human system.

Force. And any object will only change when it is subjected to external forces.

Change your own state of movement.

A: If there is no gravity, the cup will not fall to the ground, but another external force will be applied parallel to the ground, so it will still break, but not on the ground. b：

Mass and weight are two completely different concepts, the mass of an object does not change, and the weight changes with gravity. C: Correct.

The person jumps, there is an upward force, but there is no resistance (gravity does not, air resistance is ignored), so leaves the earth. D: The direction of the force comes from the arm, but the arm is connected to the body, which is like a circle, and it is impossible to leave the earth even without gravity.

Option A Because there is no gravity, it's like everything floating in the air in weightlessness in space, and the glass flies as soon as it is thrown out, so it won't break. b The mass of an object is a property of matter that does not change c Under the weightlessness of the universe, astronauts would not have flown so far, right?

c because gravity is 0!No density in the air! So buoyant!

a(b is a property of matter and cannot be changed; c, d is not likely to happen).

The selection is related to the impulse. b can be refuted according to the law of conservation of mass. c is the action and reaction force. d doesn't quite explain.

Option C On the surface of the earth, gravity is the attraction of the earth to people, and people can easily leave the earth without gravity.

a. The force in the horizontal direction b. The mass is the property of the substance d. The force that grasps the hair is the force inside the person, there is no external force, and it does not affect the state of movement.

The mass of the object lying on the liquid is equal to the volumetric mass of the liquid discharged, so the depth is directly proportional to the mass of the bottle sand and inversely proportional to the density of the liquid. I need to explain the specific calculation.

The arrangement of option b is as follows: the valency of chlorine increases sequentially.

The valencies of chlorine elements in HCl, Cl2, HCO3 and HCl4 were -1, 0, +5 and +7, respectively

Therefore, the valency of chlorine in the brackets is between 0 and +5.

The valency of chlorine in HCro is +1, so B is chosen

The oxidation of d is gradually enhanced from hydrochloric acid to perchloric acid.