Question

a swimmer of mass 55 kg jump from the edge of a cliff 30 m high. Touching the water 3 s after launch, what is the value of the frictional force exerted by the air on the swimmer?

Answer 1

let first just get the acceleration which the body have to reach the pool.
\[x =0.5 a t ^{2}\]
\[a= 2x /t ^{2} = 2* 30 /9 = 6.6667\]
Now the Total force is the result of subtraction between the resistance and gravity because
so the resultant force is the follwoing
\[F total = Fg - Fresis.\]
\[ma = mg - Fresis\]
\[Fresis = m(g-a) = 55 (9.8 - 20/3) = 172.333\approx 172.3 N.\]