Question

The velocity of a diver just before hitting the water is -7.7 m/s, where the minus sign indicates that her motion is directly downward. what is her displacement during the last 0.82 s of the dive?

Answer 1

The velocity of a diver just before hitting the water is -7.7 m/s ( i.e final velocity
`v_(f) = -7.7 m/s` ).

Therefore velocity of diver before 0.82 s,

`v_(i) =v_(f) +gt= -7.7m/s+9.8m/s^2(0.82 s) =0.34 m/s`.

Now the displacement during the last 0.82 s of the dive, from the vertical motion,

`s=v_(i)t -(1)/(2) gt^2=(0.34m/s)*(0.82s)-(1)/(2)(9.8m/s^2)*(0.82s)^2\\\\ s = -3.0 \ m`

Thus, the displacement is 3.0 m in downward.