What is the velocity of the rock when it is 5.10m5.10m below the starting point (remember that velocity is a vector)?

Question

A person throws a rock straight downwards off a cliff with an initial speed of 13.0m/s13.0m/s. What is the velocity of the rock when it is 5.10m5.10m below the starting point (remember that velocity is a vector)? Treat the effect of air resistance to be negligible and the upwards direction as positive.

Answer 1

v_y² = v_yo² + 2a_yΔy (assuming constant acceleration)

v_yo = -13 m/s

a_y =-9.8 m/s²

^{Δy = - 5.1 m}

^{when you solve for the velocity after traveling 5.1 m downward the direction of motion will be down. This function gives the speed because the velocity is squared and direction must be inferred. Your answer must be negative and more then 13 m/s because speed will increase during descent.}

^{Solve for} v_y and record your answer with a neg sign because they said up was positive. Good luck.