Relationship between velocity of wheel and car

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SUMMARY

The discussion centers on the relationship between the angular velocity of a wheel and the linear velocity of a car powered by a falling mass. The equation mgh = 0.5*I*w² is utilized to derive the angular velocity, while the total energy of the car must account for both the translational kinetic energy and the rotational kinetic energy of all four wheels. The correct formulation is mgh = 0.5*m*v² + 4*0.5*I*w², indicating that the linear speed of the car can be derived from the rotational speed of the wheels using the relationship v = w*r.

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  • Familiarity with rotational dynamics, including moment of inertia (I).
  • Knowledge of kinematic relationships between linear and angular motion.
  • Ability to manipulate and solve equations involving multiple variables.
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  • Study the principles of energy conservation in mechanical systems.
  • Learn about the moment of inertia and its calculation for different shapes.
  • Explore kinematic equations that relate linear and angular velocities.
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Physics students, mechanical engineers, and hobbyists designing vehicles or experiments involving rotational motion and energy conversion.

dan38
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So I've designed a car which is powered by a falling mass.
Using Energy Questions, i.e. mgh = 0.5*I*w2
I've worked out the angular velocity of the wheel; so my question is whether this represents this velocity of the whole car or do I need to multiply this value by 4?
 
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hi dan38! :smile:

(try using the X2 button just above the Reply box :wink:)
dan38 said:
Using Energy Questions, i.e. mgh = 0.5*I*w2
I've worked out the angular velocity of the wheel; so my question is whether this represents this velocity of the whole car or do I need to multiply this value by 4?

your RHS needs to be the total energy of the car, ie 4 times the rotational kinetic energy of each wheel, plus the ordinary translational kinetic energy of the car-plus-wheels :wink:
 
ohh i see, so basically we have mass attached to a string connected to a rotating skewer with two wheels on either side.
so my workings would be:
mgh = 0.5*m*v2 + 4*0.5*I*w2

Where v = Speed of Car and m = Mass of Car
w = Rotational Speed of Wheels

And by figuring out the speed of the string, I can use the relationship v = w*r to find "w" of the wheel?
:D
 

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