Ok, assuming "mj" in the question is Megajoules MJ) you need a total amount of rotational kinetic energy in the fly wheel at the beginning of the trip that equals
(2.4e6 J/km)x(300 km)=7.2e8 J
The expression for rotational kinetic energy is
E = (1/2)Iω²
where I is the moment of inertia of the fly wheel and ω is the angular velocity.
So this comes down to finding the value of I that gives the required energy. We know the mass is 101kg. The formula for a solid cylinder's moment of inertia is
I = (1/2)mR²
We want (1/2)Iω² = 7.2e8 J and we know ω is limited to 470 revs/sec. However, ω must be in radians per second so multiply it by 2π to get
ω = 2953.1 rad/s
Now let's use this to solve the energy equation, E = (1/2)Iω², for I:
I = 2(7.2e8 J)/(2953.1 rad/s)² = 165.12 kg·m²
Now find the radius R,
165.12 kg·m² = (1/2)(101)R²,
√(2·165/101) = 1.807m
R = 1.807m
Answer:42.43m/s
Explanation:According to vf=vi+at, we can calculate it since v0 equals to 0. vf=0+9.8m/s^2*4.33s= 42.434m/s
<h2>
It takes 6.78 seconds to complete 12 dribbles.</h2>
Explanation:
Frequency of dribble = 1.77 Hz
That is
Number of dribbles in 1 second = 1.77
Now we need to find how long does it take for you to complete 12 dribbles.
Time taken for 12 dribbles = 12 x Time taken for 1 dribble
Time taken for 12 dribbles = 12 x 0.565
Time taken for 12 dribbles = 6.78 seconds
It takes 6.78 seconds to complete 12 dribbles.
The air would contract therefore the answer is the second choice.
