Answer:
<h2>The answer is 90 kg</h2>
Explanation:
In order to find the mass of the football we use the formula

where
p is the momentum
v is the velocity
We have

We have the final answer as
<h3>90 kg</h3>
Hope this helps you
If the impulse is 25 N-s, then so is the change in momentum.
The mass of the ball is extra, unneeded information.
Just to make sure, we can check out the units:
<u>Momentum</u> = (mass) x (speed) = <u>kg-meter / sec</u>
<u>Impulse</u> = (force) x (time) = (kg-meter / sec²) x (sec) = <u>kg-meter / sec</u>
Answer:
Their experimental design lacks control group
Explanation:
Based on what I read, the scientists don't have a control group as one of the main groups thus they cannot, in scientific sense, say that the medicine is better or worse. You always need a control group receiving no intervention because then we can compare groups and assess the effectiveness of that intervention (in our case if we had control group vs people who received the medicine, we could see if the people who received the medicine had improved condition etc when compared to participants who did not receive anything)