Question

When landing after a spectacular somersault, a 45.0 kg gymnast decelerates by pushing straight down on the mat. Calculate the force she must exert if her deceleration is 8.00 times the acceleration of gravity.?

Answer 1

So the force that the gymnast with a mass m=45 kg, has to exert against the ground to stop if her acceleration is a=8*g, where g=9.81 m/s², can be obtained from the Newtons second law: F=m*a, where F is the force, m is the mass and a is acceleration. 

F=m*a=m*8*g=45*8*9.81=3531.6 N. 

So the force that a gymnast has to exert on the mat in order to stop is F=3531.6 N.