4. A 5.00-kg sled starts at rest and accelerates down a 45.0° incline. The coefficient of kinetic friction between the mass and the incline is .185.
a) What is the value of the of the acceleration of the sled

The image below shows numerous volcanic mountains in the pacific northwest. what is the most likely cause of the volcanic and earthquake activity in this region?

It is really hard for me right know

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve