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hi there, i was wondering if anybody could help me with some problems i am having great difficulty getting my head around at the minute, any help would be greatly appreciated.
The first question is:
A piledriver hammer of mass 150kg falls freely through a distance of 5m to strike a pile of mass 400kg and drives 0.075m into the ground. the hammer does not rebound when driving the pile. Determine the average resistance of the ground.
The second question is linked to the first and is: Compare and contrast the use of D'Alembert's principle with the principle of conservation of energy when solving the problem given above.
so far i have used linear equations to work out the striking speed of the hammer. using:
s = 5m
a = 9.81m/s (gravity)
u = 0m/s (initial velocity)
i worked out v in the equation v(squared) = u(squared) + 2as. this came to 9.905m/s (striking speed)
i then put this value into v = u + at. and found t = 1second.
my next step was to find the resistance force when the hammer has struck the object and now they are moving together.
u = 9.905m/s (striking speed)
v = 0m/s (stops dead)
s = 0.075m (distance it goes into the ground)
i found a using v(squared) = u(squared) + 2as. this came to -654.06m/s
and t using v = u + at. this came to 0.015seconds.
i then used the resistance force equation F=ma. 550 x -654.06 = -349.733kN
this was quite straight forward after a few steps back to think about it, but I am not sure if i have done the right process.
v = u+at
V(squared) = U(squared) + 2as
F = ma
I = mv - mu
I = Ft
if this is correct, then the main problem for me is to work out the next stage of the question which is using the principle of conservation of energy. It has me really stumped because we don't have an example to follow that is similar, or anything even closely linked to it that we may use.
any help would be greatly appreciated, even just to clarify that my first question is correct.
thankyou all in advance
Homework Statement
The first question is:
A piledriver hammer of mass 150kg falls freely through a distance of 5m to strike a pile of mass 400kg and drives 0.075m into the ground. the hammer does not rebound when driving the pile. Determine the average resistance of the ground.
The second question is linked to the first and is: Compare and contrast the use of D'Alembert's principle with the principle of conservation of energy when solving the problem given above.
so far i have used linear equations to work out the striking speed of the hammer. using:
s = 5m
a = 9.81m/s (gravity)
u = 0m/s (initial velocity)
i worked out v in the equation v(squared) = u(squared) + 2as. this came to 9.905m/s (striking speed)
i then put this value into v = u + at. and found t = 1second.
my next step was to find the resistance force when the hammer has struck the object and now they are moving together.
u = 9.905m/s (striking speed)
v = 0m/s (stops dead)
s = 0.075m (distance it goes into the ground)
i found a using v(squared) = u(squared) + 2as. this came to -654.06m/s
and t using v = u + at. this came to 0.015seconds.
i then used the resistance force equation F=ma. 550 x -654.06 = -349.733kN
this was quite straight forward after a few steps back to think about it, but I am not sure if i have done the right process.
Homework Equations
v = u+at
V(squared) = U(squared) + 2as
F = ma
I = mv - mu
I = Ft
if this is correct, then the main problem for me is to work out the next stage of the question which is using the principle of conservation of energy. It has me really stumped because we don't have an example to follow that is similar, or anything even closely linked to it that we may use.
any help would be greatly appreciated, even just to clarify that my first question is correct.
thankyou all in advance