# College Physics Problem 2.17

#### Dr. John Paul Stapp was U.S. Air Force officer who studied the effects of extreme deceleration on the human body. On December 10, 1954, Stapp rode a rocket sled, accelerating from rest to a top speed of 282 m/s (1015 km/h) in 5.00 s, and was brought jarringly back to rest in only 1.40 s! Calculate his (a) acceleration and (b) deceleration. Express each in multiples of $g\:\left(9.80\:\right)m/s^{2}$ by taking its ratio to the acceleration of gravity.

SOLUTION:

A) The formula for acceleration is

$a=\frac{v_f-v_{0\:}}{t}$

Substituting the given values

$a=\frac{282\:\frac{m}{s}-0\:\frac{m}{s}}{5.00\:s}$

$a=56.4\:m/s^{2}$

B) The deceleration is

$a=\frac{0\:\frac{m}{s}-282\:\frac{m}{s}}{1.40\:s}$

$a=-201.43\:m/s^{2}$

In expressing the computed values in terms of g, we just divide them by 9.80.

The acceleration is

$\frac{56.4}{9.80}=5.76g$

The deceleration is

$\frac{201.43}{9.80}=20.55g$

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