Saturday, November 7, 2009

Rate of Change of Momentum

1. Newton's 2nd law states that the rate of change of momentum is directly proportional to the resultant force, and in the same direction as the force.

2. Newton is a smart guy, so his sentences and laws are always in proper English. But, for the rest of us, what the hell is he trying to say? Let's brake it down into pieces.

3. First, lets understand momentum. Momentum is the mass of something times its velocity. In reality, we're just trying to explain movement. A car and a lorry are moving at the same speed on the highway. So, which one is, well, boleh bergerak dengan lebih mudah?Apabila sesuatu benda lebih berat, benda itu akan lebih susah untuk berhenti apabila ia dalam keadaan bergerak. Back to the car and the lorry, which one has more momentum? Because the lorry is heavier than the car, and their velocity is the same, the lorry will have more momentum. It will be more difficult to make the lorry stop compared to the car, even if they are moving at the same speeds. Get the idea?

4. So, Newton suggested that, the rate of change of momentum, i.e, how much the momentum increases or decreases per given time, is directly proportional to the resultant force, i.e, the final force, or the end force.

5. Basic idea here is, if the rate of change of momentum is high, you will get more force.

6. If the rate of change of momentum is low, you will get less force. They are directly proportional.

7. So, if you want a large amount of force, you must increase the rate of change of momentum. If you want little force, you must lower the rate of change of momentum.

8. Rate of change of momentum increases if there is a large increase or decrease of momentum in a given time. Also, if you decrease the time while keeping the momentum constant, the rate of change of momentum also increases.

9. In situation A, there is a momentum of 10 kg m s-1 per 10 seconds. In situation B, there is a momentum of 10 kg m s-1 per 5 seconds. So, the rate of change of momentum in B is higher than in A.

10. This is what impulsive force is all about.

No comments:

Post a Comment