momentum change in impluse

[badkins]

how to set up this problem to solve . Mathematically, ?p = F?t.We will be bringing objects to a halt and will find that, for a given ?p, not all F?t's are the same (think of the bungee jumper). Here's another situation. A car going 30 mph hits a brick wall which stops the car instantly. Very dangerous! Now think of that same car hitting a large bale of hay and comming to a stop in about 3 seconds. No problem. Same impulse ( ?p), but not the same result! Why not? (The answer lies in the right hand side of the above equation.)

change in p is 30 mph
velocity is 0
time is 3/s
30x 3= 90

 

[royhaas]

Momentum is not the derivative of force with respect to time. It's the derivative of work or energy with respect to velocity. I assume you are talking about Newtonian mechanics. Momentum is the integral of force with respect to time.

 

[badkins]

Can you tell how to setup this problem I still don't understand. I haven't did math in 20 years and I am taking a science class to get my degree and this is one of the required course. I didn't realize that I had to perform math equations in this course. I did algebra 20 years am I don't remember this type of questions

thanks

 

[Deleted member 4993]

how to set up this problem to solve . Mathematically, ?p = F?t.We will be bringing objects to a halt and will find that, for a given ?p, not all F?t's are the same (think of the bungee jumper). Here's another situation. A car going 30 mph hits a brick wall which stops the car instantly. Very dangerous! Now think of that same car hitting a large bale of hay and comming to a stop in about 3 seconds. No problem. Same impulse ( ?p), but not the same result! Why not? (The answer lies in the right hand side of the above equation.)

change in p is 30 mph
velocity is 0
time is 3/s
30x 3= 90

?p = F?t

F = ?p/?t

Change of momentum (?p) is same for both cases. So, F(orce) is inversely proportional to the "time of impact" (?t). Thus as ?t decreases - F increases.