Physics Lect 4

Momentum
- p = mv
- in an isolated system momentum is always conserved
- a vector
Collisions are either:
- 1) Elastic - mechanical energy is conserved, all E is transferred between objects
- 2) Inelastic - momentum is conserved, some E is transferred to internal E
Completely Inelastic Collisions

Stick together and p_i = p_f
Solving Inelastic Collisions

draw 2 systems: 1 right before the collision and one right after
Reverse Collisions
- Start from rest and then burst apart
- p_i = p_f = 0
- in order to conserve momentum they must sep. in exactly opp. directions
- ineslastic
What is nec. in order for an object to "bounce back" after it has struck another object?

It must have less mass than the object it has hit
Impulse
- Change in Momentum
- J = Δp = Δmv or J = F_ave Δt
- this states that if the time over which a force acts is increased, the same Δv can be achieved (how airbags reduce force on a passenger)
Machines
- Reduce the amount of F needed to do work but does not change the amount of W
- Ramp, Lever, Pulley: all F proportional to 1 / d
Radioactive Decay
- All atoms undergo decay except H
- 1:1 prot:neut ratios help to stablize smaller atoms
Alpha Decay
- ⁴₂ a
- emitted
- R side of arrow

Author

laskiru

58879

Card Set

Physics Lect 4

Description

Momentum, Machines, Radio Active Decay

Updated

2011-01-10T03:25:01Z

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