During the process of mountain building, earthquakes sometimes occur along continental-continental convergent boundaries. Which statement best describes the motion of the plates along these boundaries that causes the earthquakes?

The plates push apart from each other with no subduction.
Subduction occurs with the less-dense plate sinking below the other plate.
Subduction occurs with the more-dense plate sinking below the other plate.
The plates smash together with no subduction.

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?