Water resources management, asset evaluation and management. Which is better, project cost (science girls)

First, there is a premise that the resultant force is proportional to the mass of the object, that is, the acceleration of the object is constant. Otherwise, let's look at a counterexample:

The mass of an object is 100kg, but its acceleration is only 0.0 1m/s? Then the external force f =1n. The mass of another object is1,but its acceleration is 1000m/s? Then his resultant force is1000 n. Then it is not proportional to the mass of the object.

Second, it is wrong to be proportional to the acceleration of an object. There must be a premise that the quality is certain. Let's give a counterexample:

The mass of an object is 10000kg, but its acceleration is only 1m/s? Then the external force f =10000 n. The mass of another object is1,but its acceleration is 1000m/s? Then his resultant force is1000 n. Then it is not proportional to the acceleration of the object.

Reminder: When discussing the direct ratio or inverse ratio in the formula F=ma, we must pay attention to whether there is a premise, otherwise we can't simply say it. Unless one of them remains the same. The other is the inherent properties of an object, such as melting point (regardless of pressure), mass (this is something that does not consider relativity, unless the topic is specifically explained in high school), gravitational acceleration (when gravity is not discussed), electric field strength, magnetic field strength, potential at a certain point in electricity, and ohmic value of resistance (unless the topic mentions that temperature affects ohmic value). Generally speaking, these values cannot be said to be directly or inversely proportional to some values.

One sentence about this topic is also correct:

From F=ma,

same

The resultant force on an object is proportional to its acceleration.

. But remember that it cannot be said to be proportional to the mass of an object, because the mass of the same object is constant. )