The eaths radius is the correct answer, if you need proof look at nasa's website
As we know that in transformers we have

here we know that



now from above equation we will have



Force exerted by Justin=300 N
Here power= 600 W
distance traveled=10 m
time=5 s
power is given by P= Work done/ time
600=work/5
so work= 60x5=3000J
now work done= force* distance
3000=F *10
F= 3000/10
F=300 N
Answer:
Magdeburg hemispheres are two half-spheres of equal size. Placing them together traps air between them. This air is merely trapped, and not compressed, so the pressure inside is the same as the pressure of the atmosphere outside the spheres. The spheres thus pull apart with nearly no resistance.
Answer:
Final velocity will be equal to 14 m/sec
Explanation:
We have given initial velocity u = 5 m/sec
Constant acceleration is given 
Time t = 6 sec
We have to find the final velocity
From first equation of motion
, here v is final velocity, u is initial velocity , a is acceleration and t is time
So 
So equal final velocity will be equal to 14 m/sec