Halley's Comet visits Earth's atmosphere once every 76 years. What branch of the Earth sciences is the main group that studies these phenomena

I'm having some difficulty seeing the diagram clearly.but the question says there's a net inward force on the object.so we know right away,  from newton's 2nd law of motion, thatthat baby is accelerating.  it doesn't even matter which way thenet force is pointing.  if there's any net force, then either theobject's speed or else its direction must be changing.

Cardiac muscle causes movement in the bone.