IIT JEE , AIEEE Forum - Physics , Mechanics

ramyani

Prof. Puerile smuggles a fire extinguisher into a skating rink. Climbing out onto the ice without any skates on, he sits down and pushes off from the wall with his feet, acquiring an initial velocity v₀ y. At t = 0, he then discharges the fire extinguisher at a 45-degree angle so that it applies a force to him that is backward and to the left, i.e., along the negative y axis and the positive x axis. The fire extinguisher's force is strong at first, but then dies down according to the equation | F | = b - ct, where b and c are constants. Find the professor's velocity as a function of time.

ps. y is unit vector along Y axis

akhil_o

I am not sure i understood the question completely...if he pushes against the wall he acquires a velcity v0 in x direction

If the professor slides only in the horizontal direction...

Fcos 45 =ma

f cos 45 = m dv/dt

or dv =f cos 45/ m dt

dv = 1/

2 m (b- ct) dt

integrating on both sides

change in velocity

v = 1/m

2 (bt-ct²/2)

hence v_t=v₀+ 1/m

2 (bt-ct²/2)

saurabh_reincarnated

ya pretty the same ans. to akhil

and if vertical force> mg

then path will be diff and thus there will be a vel. in vertical and resultant wil be vectr. sum of these.........

ramyani

that is not the answer.

I m telling u the source. I got this solved problem in lightandmatter.com .

the site was referred bu a member in this goiit.

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