A crow flies forward and backward. Its motion is shown on the following graph of horizontal position x vs. time t.
What is the instantaneous velocity of the crow at t = 9 s ?

What if? if the temperature near the cliff suddenly falls to 0°c, reducing the speed of sound to 331 m/s, what would the initial speed of the rock have to be (in m/s) for the soccer player to hear the sound of the splash 2.90 s after kicking the rock?

Ababy stroller is a rest on top of a hill which is 10 m high. the stroller and baby have a mass of 20 kg. what is the potential energy of the baby and stroller?

Which is not true about oxygen-17 and oxygen-18?