Question

an athlete thrown a javelin of mass 800g distance of 87.58m what is the force applied on it and what is the initial velocity with which it thrown

Answer 1

You can't answer this question many things are not mentioned like angle of projection, time span just giving the Mass and distance it traveled won't help you to get the answer you are asking for. Assuming it to be thrown at 45 degrees which is the ideal Condition to throw something at the maximum range. We have the angle of protection do simple calculation

v×cos45° = 87.58 you will get the velocity.

And now let's talk about the acceleration it will be v× root 2 multiplied by mass .. that's the answer .