The final speed of the toy car at the end of the given time period is 3.58 m/s.
The given parameters;
- distance traveled by the car, s = 1.2 m
- time of motion of the car, t = 0.67 s
- initial velocity of the car, u = 0
The acceleration of the car is calculated as;

The final velocity of the toy car is calculated as;

Thus, the final speed of the toy car at the end of the given time period is 3.58 m/s.
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When you exert a force on the coin, it will accelerate. If you push the coin and it moves at a constant velocity, the friction force must be equal to the force that you are exerting. This is an example of a balanced force. When the net force is greater than 0 N, the is an unbalanced force.
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:
E=hf
Were, h = Planck constant 6.67*10^11
E=3.8*10^24 * 6.67*10^11= 2.508*q0^36j