Topic content:
The correct statement about gravity is ()
A. When falling to the earth, the gravity of the object is greater than that of the object at rest
B. Since the direction of gravity is always vertically downward, gravity must be perpendicular to the ground
C. Gravity is the pressure of objects on the horizontal table
D. Whether an object is stationary or moving, and no matter how it moves, the gravity it receives is the same
Best answer:
Gravity G=mg has nothing to do with whether or not it is subjected to other forces, and has nothing to do with the motion state, so A is wrong;
B、 The direction of gravity is vertical downward, but not necessarily vertical to the ground, so B is wrong;
C、 The force applying object of gravity is the earth, and the force applying object of pressure is the object, not the same force, so C is wrong;
D、 Gravity G=mg has nothing to do with whether it is subjected to other forces, nor with the motion state, so D is wrong
Therefore, D is correct
Answer analysis:
There is no explanation for this question
Test core:
Gravity:
1. The generation of gravity: objects near the ground are attracted by the earth, which is called gravity. All objects near the ground are subject to gravity, which is called weight for short. The unit of gravity is N, but the symbol is G. explain:
(1) It is caused by the gravity of the earth, but it cannot be said that gravity is the gravity of the earth. M is the mass of the object, and g is the acceleration of gravity. Generally, 9.8N/kg (9.8m/s2) is taken, meaning that 9.8N is applied to each kilogram of mass.
(1) Gravity at the two poles is equal to universal gravitation, universal gravitation at the equator=gravity+centripetal force (2) When the earth rotation is not considered, gravity can be considered equal to universal gravitation (3) Generally, the higher the latitude is, the greater the g value is (4) It has nothing to do with the motion state of the object. 3. The direction of gravity: the direction is always vertical downward, not necessarily pointing to the center of the earth (only at the equator and the poles pointing to the center of the earth).
(1) It does not necessarily point to the center of the earth, but only at the poles or equator. (2) The direction of gravity points to the center of the earth, The center is at its geometric center (3) The center of gravity is not necessarily on the object (4) The position of the center of gravity is independent of the motion state, spinning mode and position of the object