Answer:
1 and 3
Explanation:
At the point of hitting the tennis ball by the racquet, the force by the hit is acting on the ball.
Since there is a strong wind, the force exerted by the air will act on the tennis ball as it journeys to the ground in the opponents court.
Also, since the tennis ball undergoes a downward motion before it touches the ground, a downward force of gravity also acts on the ball.
After the tennis ball has left contact with the racquet, the force by the hit ceases to act on the ball since they are no longer in contact. However, <em>the downward force of gravity and the force exerted by the air still act on the tennis ball before it touches the ground. </em>
Therefore, the correct choice is:
1 and 3
The answer is a. divided by time
Answer:
Explanation:
element usual oxidation state exceptions
Group 2 metals always +2
Oxygen usually -2 except in peroxides and F2O (see below)
Hydrogen usually +1 except in metal hydrides where it is -1
Fluorine always -1
Answer: 0.002 newtons
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Work Shown:
I'm assuming you meant to write "at 20 m/s^2" at the end. If so, then,
0.10 grams = 0.10/1000 = 0.0001 kg
m = 0.0001 kg = mass
a = 20 m/s^2 = acceleration
F = ma .... newton's second law
F = 0.0001*20
F = 0.002
The force required is 0.002 newtons
Kinetic Energy = (1/2) (mass) (speed)²
KE = (1/2) (400 kg) (50 m/s)²
KE = (200 kg) (2500 m²/s²)
KE = 500,000 kg-m²/s²
<em>KE = 500,000 Joules</em>
KE = 1/2 Mega-Joule