Answer:
8) d
9) c
<em>Hope this helps! :)</em>
Answer:
Force, F = 900 N
Explanation:
Given that,
Mass of the football, m = 0.55 kg
Initial speed of the ball, u = 0
Final speed, v = 54 m/s
Time of contact, t = 0.033 s
We need to find the magnitude of the force exerted by the ball on the kicker’s foot. It is a case of second law of motion. It is equal to the rate of change of momentum. So,

So, the magnitude of the force exerted by the ball on the kicker’s foot is 900 N.
Answer:
Produces heat in various parts of machines.
Due to friction we have to exert more power in machines.
It opposes the motion.
Due to friction, noise is also produced in machines.
Due to friction, engines of automobiles consume more fuel which is a money loss.
Explanation:
Source: https://www.quora.com/What-are-the-disadvantages-of-friction
Well,
One possibility is that there is much salt in the water, enough so that the sphere of steel floats.