How much force is needed to stop a 100 kg football player if he decelerates at 20 m/s-2

We know, f = ma
Here, m = 100 kg
a = 20 m/s²

Substitute their values, 
f = 100 * 20
f = 2000 N

In short, Your Answer would be 2000 N

Hope this helps!

Answer: it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.explanation:   we have equation of motion ,where s is the displacement, a is the acceleration, u is the initial velocity and t is the time taken.average velocity = displacement/ time taken.average velocity = 10.69 miles/hr = 10.69*1.6*1000/(60*60) = 4.75 m/s4.75 = s/ts = 4. 1we also have acceleration = 2.18 m/s², initial velocity = 0 m/sso it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.

Good moring let me you on this question the answer the electric force  have a good day ; )