A teacher bangs his ruler on his desk with a force of 15 N breaking it into pieces. If the ruler has a mass of 0.25 kg, how much force did the desk apply back to the ruler when it broke into pieces?

Will you chech and finish these for me, because i am stumped with them.

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?

Explain why you think this diagram shows what happened to the carbon in the biodome.