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I don't get anywhere near their answers for (a) or (b).freshbox said:yes but not for c and d
NascentOxygen said:I don't get anywhere near their answers for (a) or (b).
I get their answers only if I change the force to 120 MN.
Ah, with that correction all of my answers now are the same as those given alongside the question.ehild said:Have you used 8000 kg as mass of the hammer? (Mg = 103 kg)
That's the net force acting. Use that to find the resistive force.freshbox said:Part C
M1=mv
=(9000)(8.82)
=79380
M2=mv
=0
I1-2=Force x Time
=(F)(0.1)
=0.1F
M1+I1-2=M2
79380-0.1F=0
79380=0.1F
F=793800 Ans Wrong
I'd say so.freshbox said:Is I1-2= Force x Time this force always the net force?
Draw a free body diagram and analyze the forces acting on the hammer+pile system.freshbox said:Can you guide me on how to use the net force to find the resistive force? Is there a formula to it?
For one thing, action and reaction forces act on different bodies. What you want are the forces acting on the hammer+pile.freshbox said:There is an action and reaction force. Action :+793800 Reaction-793800
That's the opposing force to bring about the deceleration. In addition, you also have to oppose their weights, as well.freshbox said:Part C
M1=mv
=(9000)(8.82)
=79380
M2=mv
=0
I1-2=Force x Time
=(F)(0.1)
=0.1F
M1+I1-2=M2
79380-0.1F=0
79380=0.1F
F=793800 Ans Wrong
What about the force you are asked to find?freshbox said:I just can't think of any other forces besides gravity..
So, what's the gravitational force? Set the sum equal to the net force.freshbox said:Yes the 2 forces are gravity and resistive force, sorry.
Forget about 'balancing' anything.How many Newtons force UP must be exerted to balance their weights acting DOWNWARD? -793800N? What are you trying to tell me, action/reaction ?
OK.freshbox said:793800=Fr-88290
Fr=793800+88290
Fr= 882090
The "G force" is just the weight of the system, which acts down. It's one of the two forces acting. It's not the net force.Ok this is the answer but I still don't understand the concept behind it.
Doc AL said, So, what's the gravitational force? Set the sum equal to the net force. I assume G Force = Net Force -> can you explain why G force is equal to net force?
The resistive force is upward (the ground pushes up), the gravitational force is downward; the net force is upward. So, taking up as positive, the gravitational force would be negative.From this equation F=Fr-G, how do you determine G force is -ve, Fr and F is both +ve because at first I tried setting it as G=F-Fr because I thought all should be positive except Fr since it is "resist"
Newton's 2nd law!freshbox said:I'm sorry I still don't understand. What acceleration got to do with netforce?
I don't quite understand your question. It is the net force on a body that determines its change in motion.freshbox said:So I1-2= Force x Time
This is the net force but what does it represent as?