Problem 5-108 Force and Kinematics - C

Tiny Tompfind, a man of mass \(72\; kg\), jumps (from rest) from a table \(92 \;cm\) to the floor below. As he lands, he bends his knees so that he decelerates over a distance of \(35 \;cm\).

(a) What is Tiny's speed just as he hits the floor?
(b) As he decelerates, what is the magnitude of the force exerted on him by the floor?

Four possible coordinate systems for Tiny Tompfind jumping.


In fact any of A, B  or C are satisfactory since nothing in the problem involves the \(x\) direction. If we choose (B) then the motion takes place in the \(+\) direction.

We need his speed just before he hits the floor. Which Galilean equation is useful?

(A)   \(v_y = v_{0y} + a_{y{^t}}\)

(B)   \(y = v_{0y{^t}} + (1/2)a_yt^2\)

(C)   \(v_y{^2} = v_{0y}{^2} + 2a_yy\)