In: Physics
(section 11-6; 11-7 in 3rd edition) A windmill with moment of inertia I is not rotating until a passing eagle grabs on to the top of it with her talons as she flies by. The "system" of interest is the eagle plus the blades of the windmill. Check all the statements that are true. All angular momentum is to be calculated relative to the center (pivot) of the windmill.
Group of answer choices
There is no angular momentum until the bird and wheel start spinning.
Linear momentum has been converted to angular momentum.
Linear momentum has been absorbed by the Earth.
There is more kinetic energy after the grab than before.
There is less kinetic energy after the grab than before.
There is more angular momentum after the grab than before.
There is less angular momentum after the grab than before.
All the statements and whether they are true or false have been tabulated below with explaination.
Statements | True / False | Explanantion |
There is no angular momentum until the bird and wheel start spinning. |
True | Angular momentum is defined as the product of moment of Inertia and angular velocity, and angular velocity is zero until the eagle sits on the windmill. So, angular momentum is zero. |
Linear momentum has been converted to angular momentum. |
True | Linear momentum of the eagle has been converted into angular momentum of the eagle plus windmill system. |
Linear momentum has been absorbed by the Earth. |
False | As the eagle sits on the windmill it starts rotating. So, linear momentum of the eagle has been converted into angular momentum of the eagle plus windmill system. So, linear momentum is not absorbed by the Earth. |
There is more kinetic energy after the grab than before. |
False |
After the grab, all the kinetic energy of eagle is converted into the rotational energy of the eagle plus windmill system. |
There is less kinetic energy after the grab than before. |
True | After the grab, all the kinetic energy of eagle is converted into the rotational energy of the eagle plus windmill system. |
There is more angular momentum after the grab than before. |
True | Before the grab there is only linear momentum which is converted into angular momentum after the grab. |
There is less angular momentum after the grab than before. |
False | Before the grab there is only linear momentum which is converted into angular momentum after the grab. |