Answer:
69.68 N
Explanation:
Work done is equal to change in kinetic energy
W = ΔK = Kf - Ki = 
W = 
where m = mass of the sprinter
vf = final velocity
vi = initial velocity
W = workdone
kf = final kinetic energy
ki = initial kinetic energy
d = distance traveled
Ftotal = total force
vf = 8m/s
vi= 2m/s
d = 25m
m = 60kg
inserting parameters to get:
W = ΔK = Kf - Ki = 



= 39.7
we know that the force the sprinter exerted F sprinter, the force of the headwind Fwind = 30N

Sample:
As soon as the lightning is seen, sound travels in the air for several kilometers until it eventually reaches the observer.
No the density does not change. Density is a ratio D=m/v no matter how much of a substance you have its mass will be proportional.
When doing density labs sometimes you might get different answers due to errors that are unavoidable.
Answer:
Explanation:
The image is real light rays actually focus at the image location). As the object moves towards the mirror the image location moves further away from the mirror and the image size grows (but the image is still inverted).