10) An object moves with a constant speed of 30 m/s on a circular track of radius 150 m. What is the acceleration of the object?
Answer is 6m/s^2
A=v^2/r
A=30^2/150= 6m/s^2

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods

there are no contact forces mentioned on the list of choices that you've provided.