What Formula Calculates the Force on a Mass by a Pole?

[benhorris]

Heres a question for you, can't work out what formula to use so i need some help.

A mass of 220KG, hits a cylindrical pole into the ground. Just before it hits the velocity of the mass is 10ms-1.

The pole is pushed 0.4 m into the ground, when the mass is droped 5m onto the pole. G = 9.8ms-2.

Show that the average force exerted by the pole on the mass is 27kN.

I just can't work it out! i know its simple but if someone can explain it to me id much appreciate it as I've spent nearly 30 mins on this one question and its only worth 2 marks..

Thanks in advance.

Ben.

 

[dextercioby]

Presumably there's no friction between the pole & the mass,so u'll have to assume that the force required will do work in pushing the pole.So the work done is equal to the KE transferred by the mass.

Daniel.

 

[benhorris]

KE =0.5mv^2

hence 0.5x220x100 = 11000 J

? Now what - stuck on this Q and its very annoying...

 

[dextercioby]

Yes,but for a collinear force,the work is simply W=F*d...

Daniel.

 

[benhorris]

Arnt i a numpty... hehe.

W=f*D
11000/0.4 =f

f =27500N

Duh, flippin ek. Always the simple ones that get me..

 

[benhorris]

Thanks by the way. I am sure i have tested your intellectual capabilities to the utmost extreme levels. ...

;-)

Thanks once again.

 

[dextercioby]

Don't worry,i had the head-ache before looking over your problem... It's just that now,i suddenly feel it more intensely...

Daniel.

P.S.OUCH!