PLEASEEE HELP I HAVE BEEN STRUGGLING FOR 2 DAYS If i workout 90 minutes on earth, if I am on a rocket traveling 0.80c, according to the timer on the rocket, how long should I exercise?

You should still workout 90 min.

The proper time is measured by a single clock in a single place.

The proper time on earth is 90 min.

The clock on the rocket is also in a single place in the frame of the rocket so you still need to workout for 90 min.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.