In the test of verifying Newton's second law, why is the mass of the heavy object much less than that of the car?

In the test of verifying Newton's second law, why is the mass of the heavy object much less than that of the car?

In the experiment of "verifying Newton's second law", it is required to measure the combined external force and the total mass of the object, and the easier it is to measure these two physical quantities, the better. Through the elaboration of "equivalent method", we already know that the pull of the rope on the car is the combined external force on the object, and this combined external force must go through a series of calculations

When studying Newton's second law, is the mass of the car far greater than the mass of the weight and plate, or the reverse? Why?

The mass of the car is much larger than that of the weight, and the friction force should be balanced
Let the mass of the car be m and the mass of the weight be m. if the mass of the weight is relatively large, then it is equivalent to the gravity of the weight as the pulling force to drive m + m two objects to accelerate, rather than the gravity of the weight as the pulling force to pull the car to produce acceleration

In Newton's second law experiment, if the mass of the car is not much greater than the total mass of the tray and weight, how to calculate the acceleration of the car?

mg=（M+m）a
M is the mass of pallet and weight, M is the mass of trolley

Each paper tape must be punched under the condition that the total mass of the car and the weight on the car is far greater than the mass of the weight (Newton's second law verification test)

First of all, we need to know that in Newton's second law f = ma, f is approximately equal to the weight of the weight of the weight. In fact, this F should be the size of the tension t between the weight and the rope between the weight, because the force knowledge of the weight mg-t = Ma
For the weight t = ma
The results show that t = MMG / (M + m) only when m > m, t ≈ mg