- #1

Karagoz

Imagine a car that weights 1000Kg. Its engine pushes it forward with a force of 3kN. So the car is accelerating at 3m/s^2 (imagine there are no friction).

After 100 seconds (the speed of car at that moment is 300m/s, very realistic), the car hits a wagon that weighs 1000Kg, that is on rest. And imagine both the car and the wagon is so hard that no deformation happens because of the hit.

From my understanding, the speed of the car doesn't decrease after the hit. But the acceleration decreases from 3m/s^2 to 1.5m/s^2. It's because:

The car and the wagon totally weights 2000Kg. The force on the car is still at 3kN.

So then the new acceleration must be: 3000N / 2000Kg = 1.5m/s^2.

Force exerted on the wagon is 1kN:

Since the wagon is accelerating at 1.5m/s^2 and weights 1000Kg, the force exerted on it must be: 1.5*1000 = 1.5kN.

And the force exerted from the wagon to the car must be equal, which is: -1.5kN (negative since the direction is opposite)

The car drives with a wagon on the front side, after some seconds the car and wagon hits another wagon. And from now the car pushes two wagons forward.

The new acceleration is 1m/s^2 (3kN / 3000Kg = 1).

The force exerted on the first wagon from the car is 1kN:

Since the first wagon is accelerating at 1m/s^2 and weighs 1000Kg, the force exerted on the wagon from the car is 1kN.

And the force exerted on the car from the wagon is -1kN.

The same is true for the second wagon too. The force exerted on the second wagon from the first wagon is too 1kN. And the force exerted on the first wagon from the second wagon is

-1kN.

Are the calculations correct?

Why is the force exerted on the car (that makes the car accelerate) is less than the force the car exerts on the first wagon?

When the wagon and the car weighs same and have same velocity and acceleration, shouldn't the force exerted on both be the equal?

And why the force exerted by the car on the first wagon (and the force exerted by the first wagon on the car) decrease when the number of wagons increase?