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- Homework Statement
- Good evening,

This question is significantly simpler than most in here, so I apologise for that!

Truck A and truck B are at rest and connected by a pin with a spring in between them. Truck A has a mass of 20kg and truck B has a mass of 10kg.

The pin is removed and the spring expands applying force to the trucks for 0.6s before falling to the ground. Truck B has a velocity of 3m/s. Truck A also rolls away.

What is the magnitude of the force applied by the spring?

- Relevant Equations
- v=u+at

F=ma

I have calculated the acceleration of truck B from v=u+at as 5ms/s. The force applied to truck B is therefore 5x10=50N.

I am unsure whether this question is poorly worded, but I feel a reasonable assumption is that the force applied to truck A would be the same as truck B, without knowing its final velocity but only knowing that it moved. I therefore believed that the total force applied by the spring was 100N.

I have been told that the answer is 50N but cannot understand why. I don't understand how if a spring can exert 50N of force on truck B it can move truck A without any additional force. I didn't know whether this was something to do with Newton's third law? However this q seems to be converting coiled spring energy to kinetic energy, something we have not yet studied.

I apologise in advance for probably butchering various physics terms, having only recently started studying the subject. I have tried to search the Internet for advice but keep getting references to hookes law which I have not yet studied and have been told is not required...

Thank you very much in advance for helping!

I am unsure whether this question is poorly worded, but I feel a reasonable assumption is that the force applied to truck A would be the same as truck B, without knowing its final velocity but only knowing that it moved. I therefore believed that the total force applied by the spring was 100N.

I have been told that the answer is 50N but cannot understand why. I don't understand how if a spring can exert 50N of force on truck B it can move truck A without any additional force. I didn't know whether this was something to do with Newton's third law? However this q seems to be converting coiled spring energy to kinetic energy, something we have not yet studied.

I apologise in advance for probably butchering various physics terms, having only recently started studying the subject. I have tried to search the Internet for advice but keep getting references to hookes law which I have not yet studied and have been told is not required...

Thank you very much in advance for helping!