Impulse and momentum (the change of force and momentum of an object)

1. Momentum: p = mv

{p: momentum (kg/s), m: mass (kg), v: speed (m/s), with the same direction as the speed. }

3. Impulse: I = ft

{I: Impulse (nos), F: Constant Force (N), T: Action Time of Force (S), and the direction is determined by F}

4. Momentum theorem: I = Δ p or ft = MVT-MVO.

{δp: momentum change δ P = MVT-MVO, which is vector type}

5. Law of conservation of momentum: p = p after the total or p'' can also be m1v1+m2v2 = m1v1'+m2v2'

6. Elastic collision: δ p = 0; δek=0

{that is, the conservation of momentum and kinetic energy of the system}

7. Inelastic collision δ p = 0; 0 & ltδek & lt； δekm

{δek: kinetic energy loss, ekm: maximum kinetic energy loss}

8. Completely inelastic collision δ p = 0; δek=δekm

{Connected into a whole after contact}

9. The object m 1 collides with the stationary object m2 elastically at the initial velocity of v 1;

v 1′=(m 1-m2)v 1/(m 1+m2)

v2′= 2m 1v 1/(m 1+m2)

10. Inferred from 9-the exchange speed (kinetic energy conservation, momentum conservation) between them in elastic collision of equal mass.

1 1. The mechanical energy loss when the horizontal velocity vo of the bullet M shoots at the long wooden block M resting on the horizontal smooth ground and is embedded in it to move together.

E loss = mvo2/2-(m+m) vt2/2 = fs relative value.

{vt:* * * * same speed, f: resistance, displacement of S relative to bullet relative to long block}

note:

(1) frontal collision is also called centripetal collision, and the speed direction is on the line connecting their "centers";

(2) The above expressions are all vector operations except kinetic energy, which can be transformed into one-dimensional algebraic operations;

(3) Condition of momentum conservation of the system: If the resultant force is zero or the system is not subjected to external force, the momentum of the system is conserved (collision, explosion, recoil, etc. );

(4) The collision process (a system composed of colliding objects in a very short time) is regarded as momentum conservation, and momentum conservation occurs when the nucleus decays;

(5) The explosion process is regarded as momentum conservation, when chemical energy is converted into kinetic energy, and the kinetic energy is increased; (6) Other related contents: recoil movement, development of rocket and space technology, and space navigation.