Chapter 7 Linear Momentum Definition For a single particle the linear momentum p is defined as: (p is a vector since v is a mV vector) So px= mvx etc Newton's 2nd Law △v△(mv) F= ma= m △p △t △t F △t Units of linear momentum are kg m/s Physics 121: Lecture 15, Pg 11
Physics 121: Lecture 15, Pg 11 Chapter 7 Linear Momentum Units of linear momentum are kg m/s. p = mv (p is a vector since v is a vector). So px = mvx etc. Definition: For a single particle, the linear momentum p is defined as: Newton’s 2nd Law:
Impulse-momentum theorem: The impulse of the force action on an object equals the change in momentum of the object FAt=4p=mv,-mv Impulse has units of Ns mpule≡FAt=Ap The impulse imparted by a force during the time interval At is equal to area under the force-time graph from beginning to the end of the time interval F △t Physics 121: Lecture 15, Pg 12
Physics 121: Lecture 15, Pg 12 Impulse-momentum theorem: The impulse of the force action on an object equals the change in momentum of the object: Ft = p = mvf – mvi Impulse Ft = p The impulse imparted by a force during the time interval t is equal to area under the force-time graph from beginning to the end of the time interval. F t t i t f t Favt F t t i t f t Impulse has units of Ns
Average Force and Impulse soft spring F Fav F tiff spring △tbig, F small △tsma av big Physics 121: Lecture 15, Pg 13
Physics 121: Lecture 15, Pg 13 Average Force and Impulse t F t F t t t big, Fav small t small, Fav big soft spring stiff spring Fav Fav
Momentum Conservation 0 EXT 0 IXI △t The concept of momentum conservation is one of the most fundamental principles in physics This is a component (vector) equation We can apply it to any direction in which there is no external force applied You will see that we often have momentum conservation even when energy is not conserved Physics 121: Lecture 15, Pg 14
Physics 121: Lecture 15, Pg 14 Momentum Conservation The concept of momentum conservation is one of the most fundamental principles in physics. This is a component (vector) equation. We can apply it to any direction in which there is no external force applied. You will see that we often have momentum conservation even when energy is not conserved. t p EXT F = = 0 t p FEXT = 0