The quantity at the left side is defined as the impulse(p na) of the force from t, to t2, and labeled as I, that is 冲量定义=F(43) Equation(4-2) becomes Fdt=mv2-mV(4-4 orI=△P=P 叫质点的动量原理
The quantity at the left side is defined as the impulse（冲 量） of the force from t1 to t2 , and labeled as , that is I Equation (4-2) becomes 2 1 2 1 I Fdt mV mV t t = = − (4-4) = 2 1 d t t I F t 冲量定义 (4-3) 叫质点的动量原理。 P P2 P1 I or: = = −
i=AP=P-p (4-2)or(4-4)is called Momentum Theorem of a particle The increment in momentum of a particle粒子动量的增量 is equal to the impulse等于作用于它的 delivered(供给) by the力的冲量。 net force Note: Eq (4-4)is a vector equation
(4-2) or (4-4) is called Momentum Theorem of a particle: The increment in momentum of a particle is equal to the impulse delivered(供给） by the net force. 粒子动量的增量 等于作用于它的 力的冲量。 P P2 P1 I = = − Note: Eq.(4-4) is a vector equation
The components of (4-4 ) are I=Fdt=ml,,-ml (45) f dt=ml2y-mViy 常用来研究碰撞问题 形t WA
The components of (4-4) are x x t t I x Fx dt mV2 mV1 2 1 = = − y y t t I y Fy t mV2 mV1 2 1 = d = − (4-5) 常用来研究碰撞问题
2 Average Force平均力( useful to collisions) collision
2. Average Force 平均力(useful to collisions) collision
as shown in the below figure the collision has finished(E4)in a very small time interval so that the force between two body is usually very great and varies rapidly(快速) with time hammer Collision between two ball workpiece For these cases, it is very useful to introduce the average force as discussed as follows
As shown in the below figure, the collision has finished（完成） in a very small time interval so that the force between two body is usually very great and varies rapidly（快速） with time. Collision between two ball workpiece hammer For these cases, it is very useful to introduce the average force as discussed as follows