Chapter 4, Problem 19P

(a)

To determine

The final velocity when a person jumps from 2.8 m high roof.

(b)

To determine

To find: Final velocity as person lands on the ground, $V_f=?$

Formula:

Third equation of motion:

  $V_f^2=V_i^2+2ad$

Where, $V_f$ is the final velocity, $V_i$ is the initial velocity, a is the acceleration and d is the displacement.

Calculation:

Substitute the vales and solve for final velocity.

  $\begin{array}{l}{V}_f^2=V_i^2+2ad\\ V_f^2=0^2+2\left(9.8\right)\left(2.8\right)\\ V_f=7.41\text{m/s}\end{array}$

c)

To determine

The average force exerted on person’s torso by his legs during deceleration.

(d)

To determine

To find: (I)Deceleration of person’s legs, $a\text{'}=?$

(II)Force on torso during deceleration, $F=?$