The formula for kinetic energy is
KE = (1/2) (mass) (speed)² .
How you measure the object's mass and speed is up to you.
You'd need different methods for different objects, and in some
cases, you'd need quite a bit of ingenuity.
Final velocity = 5km/sec = 5000 m/sec
Initial velocity = 0, mass = 5kg and force = 500,000 N
F = m(Vf-Vi)/time
Time = m(Vf-Vi)/force = 5*5000/500000 = 0.05 seconds
So, it takes 0.05 sec to arrive at the speed of 5km/s.
Answer:
- The separation will be spacelike.
- The first event can't cause the second event, as there exist an frame of reference in which both happens at the same time, in different positions, so, if there were causally connected, it will imply an instant connection, this is faster than light.
Explanation:
We can define the separation between two events (using the + - - - signature) as :

where the separation will be lightlike if is equal to zero, timelike if is positive and spacelike if is negative.
For our problem








So the separation will be spacelike, and the first event can't cause the second event, as there exist an frame of reference in which both happens at the same time, in different positions, so, if there were causally connected, it will imply an instant connection, this is faster than light.
The runner has initial velocity vector

and acceleration vector

so that her velocity at time
is

She runs directly east when the vertical component of
is 0:

It's not clear what you're supposed to find at this particular time... possibly her position vector? In that case, assuming she starts at the origin, her position at time
would be

so that after 10.4 s, her position would be

which is 19.9 m away from her starting position.