Asound wave travels across a 2,100-meter wide valley in 7.0 seconds.

How are period and frequency related to each other? dperiod is the reciprocal of frequency.

The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water

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.