# describe abt cololision of a small body with a rigid body......... plz give me ur contact no. or call me on this no. sailesh arya 9407941245

SAGAR SINGH - IIT DELHI
879 Points
11 years ago

Dear student,

It is difficult to analyse the situation when the colliding objects are free to both rotate and move with a linear motion. The main method we will use to do this involves the following stages.

1. Determine the collision point and the normal direction at this point.
2. Calculate the minimum impulse to prevent the objects intersecting, or to
reverse the approach velocity, depending on the coefficient of friction.
3. Calculate the effect of this impulse on the rotation and linear motion
separately.

This involves a lot of assumptions and approximations that may not always be valid, we need to understand what is going on to be sure that our simulations or programs are making the correct assumptions and that the results will be stable and accurate enough.

This method is based on the concept of an 'impulse' which is an instantaneous transfer of momentum between the objects. This is not intuitively obvious and I think its worth taking some time to rid ourselves of our natural misconceptions. The collision may involve an exchange of energy between the objects but the impulse is about momentum not energy, this distinction means:

• Momentum is a vector quantity in which all the dimensions are independent and the linear dimensions are independent of the rotational dimensions.
• Linear momentum and rotational momentum for a closed system are conserved independently, that is, linear momentum cannot be converted to rotational momentum and visa versa. Energy can be converted into other forms.
• The component of momentum in each dimension for a closed system is conserved independently, that is, the x component of momentum cannot be converted to, or from, the y component of momentum. Again energy can be converted into other forms.
• The whole of the impulse causes changes the linear momentum and rotational momentum, it is not that part of the impulse applies to linear momentum and the rest applies to rotational, all the impulse applies to both. In the case of energy we can ascribe part of the energy to the linear motion and another part to the rotational motion and energy can be transferred between them.

All the best.

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