haruspex said:
kashan123999 said:
technician said:
kashan123999 said:
tiny-tim said:hi kashan123999!
it means causing the bear to fall to the ground
(ie, not because it's injured but because the force actually pushes it over)
the second (energy) explanation is just plain wrong …
knocking the bear over is all about momentum, not energy
the first (force) explanation is also just plain wrong …
knocking the bear over is all about momentum, not force
also, the first explanation isn't really an explanation, since it doesn't mention what ∆p is in each of the two cases
what is ∆p ?
kashan123999 said:
tiny-tim said:
mfb said:
kashan123999 said:
tiny-tim said:nooo …
won't the rubber bounce?
kashan123999 said:
tiny-tim said:maybe?!
rubber is famous for bouncing!
btw, don't call me "sir" … i'm only a little goldfish!
'fraid so!
ok, think … what is ∆p if it bounces?
:shy:kashan123999 said:Δp = Final - original momentum=Final will be less than original, thus Delta P will be negative
tiny-tim said:
kashan123999 said:
tiny-tim said:no, 45 m/s south is minus 45 m/s north
tiny-tim said:(just got up :zzz:)
what is 50 m/s north minus minus 45 m/s north ?
kashan123999 said:
… and that's what we mean by vector addition …tiny-tim said:yes
we find the change in momentum by subtracting the 45 south vector from the 50 north vector …
since they're in opposite directions, that means we subtract minus 45 from 50, giving 95 (times the mass) as the total change in momentum
tiny-tim said:
Lead mass m with initial momentum mv, stopped dead by wall. What is its final momentum. So what is its change in momentum?kashan123999 said:
haruspex said:
…I was trying hard not to confuse you on this. You can think in terms of speeds or in terms of velocities. Because all the movement is in the same straight line, but in opposite directions, the difference is how the sign is handled. In my previous post I defined u as a speed, but you seem to be using velocities, so I'll stick with that.kashan123999 said:
tiny-tim said:
Impulse and momentum are both physical quantities that describe the motion of an object. However, impulse is the change in momentum over a certain period of time, while momentum is the product of an object's mass and velocity. In other words, impulse is a force acting on an object for a specific amount of time, while momentum is a measure of an object's inertia and how difficult it is to change its motion.
Impulse and momentum are closely related through Newton's Second Law of Motion, which states that the net force acting on an object is equal to the rate of change of its momentum. This means that the impulse acting on an object is equal to the change in its momentum. In mathematical terms, impulse (J) is equal to the change in momentum (Δp), or J = Δp.
One example of impulse and momentum in everyday life is a game of billiards. When a cue ball strikes a stationary ball, the cue ball's momentum is transferred to the stationary ball, causing it to move. The force of the cue ball acting on the stationary ball for a short period of time is the impulse that changes the stationary ball's momentum, causing it to move in a different direction.
Impulse can affect the motion of an object in several ways. If a large impulse is applied to an object over a short period of time, it can cause a significant change in the object's momentum and therefore its motion. On the other hand, a smaller impulse applied over a longer period of time may result in a smaller change in momentum and a slower change in motion. Additionally, an impulse applied in the opposite direction of an object's motion can cause it to slow down or even change direction.
In the SI system, impulse is measured in Newton-seconds (N·s) and momentum is measured in kilogram-meters per second (kg·m/s). In the English system, impulse is measured in pound-seconds (lb·s) and momentum is measured in slug-feet per second (slug·ft/s). These units can also be expressed as force multiplied by time (N·s = kg·m/s) and mass multiplied by velocity (kg·m/s = kg·m/s).