AP Physics I Study Guide Chapter 7 - Impulse &...
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AP Physics I Study Guide Chapter 7: Momentum & Impulse Momentum and forces Momentum is shown by the symbol p = / Units Momentum is a vector Direction depends on velocity More p means more difficult to stop Changing momentum (called impulse) ∆ = ! − ! To change momentum force is required • = Having acceleration means there is a change in velocity • = ∆ • ∆ = ! − ! • ! − ! = ∆ ♦ Impulse momentum theorem • = • = ! ! • = Elastic collision Kinetic energy is conserved • Only way if something is elastic • ! ! ! !! ! + ! ! ! !! ! = ! ! ! !! ! + ! ! ! !! ! ♦ MUST be true ♦ ! ! − + = ! − ! ♦ ! !! ! − ! !! ! = ! !! ! − ! !! ! ♦ ! !! ! − !! ! = ! !! ! − !! ! ♦ ! !! − !! !! + !! = ! !! − !! !! + !! ♦ ! !! + ! !! = ! !! + ! !! ♦ ! !! − !! = ! !! − !! ♦ ♦ ! ! ! !! !! !! ! !! !! !! ! ! ! !! !! !! = ! ! ! !! !! !! ! !! !! !! ! ! ! !! !! !! ♦ = !! + !! = !! + !! Perfectly inelastic Move together in the final situation ! !! + ! !! = ! ! + ! Two dimensional collisions ∆ ! = 0 ∆ ! = 0 Center of mass
Transcript of AP Physics I Study Guide Chapter 7 - Impulse &...
AP Physics I Study Guide Chapter 7: Momentum & Impulse v Momentum and forces
Ø Momentum is shown by the symbol p Ø 𝑝 = 𝑚𝑣 Ø 𝑘𝑔 𝑚/𝑠 Units Ø Momentum is a vector
§ Direction depends on velocity Ø More p means more difficult to stop Ø Changing momentum (called impulse)
§ ∆𝑝 = 𝑚𝑣! −𝑚𝑣! § To change momentum force is required
• 𝐹 = 𝑚𝑎 Having acceleration means there is a change in velocity • 𝑖𝑚𝑝𝑢𝑙𝑠𝑒 = 𝐹 ∆𝑡 • ∆𝑝 = 𝑚 𝑣! − 𝑣! • 𝑚𝑣! −𝑚𝑣! = 𝐹∆𝑡
♦ Impulse momentum theorem • 𝐹 = 𝑚𝑎 • 𝐹 = 𝑚 !
!
• 𝑡 𝐹 = 𝑚𝑣 Ø Elastic collision
§ Kinetic energy is conserved • Only way if something is elastic • !
!𝑚!𝑣!!! +
!!𝑚!𝑣!!! =
!!𝑚!𝑣!!! +
!!𝑚!𝑣!!!
♦ MUST be true ♦ !
!𝑤𝑖𝑙𝑙 𝑎𝑙𝑙 𝑐𝑎𝑛𝑐𝑒𝑙 𝑎𝑛𝑑 𝑏𝑒𝑐𝑎𝑢𝑠𝑒 𝑎 − 𝑏 𝑎 + 𝑏 = 𝑎! − 𝑏!
♦ 𝑚!𝑣!!! −𝑚!𝑣!!! = 𝑚!𝑣!!! −𝑚!𝑣!!! ♦ 𝑚! 𝑣!!! − 𝑣!!! = 𝑚! 𝑣!!! − 𝑣!!! ♦ 𝑚! 𝑣!! − 𝑣!! 𝑣!! + 𝑣!! = 𝑚! 𝑣!! − 𝑣!! 𝑣!! + 𝑣!! ♦ 𝑚!𝑣!! +𝑚!𝑣!! = 𝑚!𝑣!! +𝑚!𝑣!! ♦ 𝑚! 𝑣!! − 𝑣!! = 𝑚! 𝑣!! − 𝑣!! ♦ 𝑎𝑛𝑑 𝑖𝑓 ♦ !! !!!!!!! !!!!!!!
!! !!!!!!!= !! !!!!!!! !!!!!!!
!! !!!!!!!
♦ = 𝑣!! + 𝑣!! = 𝑣!! + 𝑣!! Ø Perfectly inelastic
§ Move together in the final situation § 𝑚!𝑣!! +𝑚!𝑣!! = 𝑣! 𝑚! +𝑚!
v Two dimensional collisions Ø ∆𝑝! = 0 Ø ∆𝑝! = 0
v Center of mass
Ø 𝑥!" = !!!!!!(!"!#$)
Ø If no external force and the system at 𝑣! is 0 m/s the center of mass stays constant
