Newton's 2nd law of motion:
Force = (mass) x (acceleration)
= (0.314 kg) x (164 m/s²)
= 51.5 newtons
(about 11.6 pounds).
Notice that the ball is only accelerating while it's in contact with the racket. The instant the ball loses contact with the racket, it stops accelerating, and sails off in a straight line at whatever speed it had when it left the strings.
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Answer:
Explanation:
Given
Power Supplied
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Efficiency of the motor 
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So, vacuum cleaner delivers a power of 
Answer:
1270 J
Explanation:
Recall that the mechanical energy of a system is the addition of the Potential energy and the Kinetic energy at any given time.
As the skier descends, potential energy is converted into kinetic energy, but the total mechanical energy should remain the same.
We see that it is not the case, so that difference is what has gone into thermal energy; 19500 J - 18230 J = 1270 J