Retarding force impacting a stationary object

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The discussion revolves around calculating the initial velocity and average resisting force for a mass dropped onto another mass. The initial velocity after impact is calculated using the conservation of momentum, resulting in a value of 3.8 m/s. The deceleration is determined using kinematic equations, yielding an acceleration of -103 m/s². The average resisting force exerted by the ground is calculated to be approximately 191,700 N. The calculations presented raise confusion among participants, particularly regarding the methodology and clarity of the math used.
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Please can you check and if i have gone wrong tell me?

Homework Statement


A mass of 150 kg is dropped onto a pile of mass 1,200kg from a height of 2.5m and drives it 7cm into the ground. calculate (a) the intial velocity of pile and driving weight immediately after impact, (b) the average reisting force exerted by the ground.
150kg
gravity 9.81
1200kg
2.5m
7cm-0.07m

Homework Equations


m1u1+m2u2=m1v1+m2v2
V²=u²+2as
F=ma
Mg-r=MA

The Attempt at a Solution


Here is my attempt not the best.

Intial velocity of pile and driving weight after impact
m1u1+m2u2=m1v1+m2v2
(1200x7)+(150x0)=(1200+150)
8400=1700

(a)v=3.8m/s combired velocity after impact

caculating deccelration

V=0m/s combined mass

V²=u²+2as

0=14.44+(2xax0.07)
0=14.44+0.14a
a=-103m/s²

Resitance

F=MA
Mg-R=MA

(b) (1700x9.8)-R=(1700x-103)
16660-R=-175100
16660+175100=R
R=191700N
 
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JamesTheEng said:
Intial velocity of pile and driving weight after impact
m1u1+m2u2=m1v1+m2v2
(1200x7)+(150x0)=(1200+150)
8400=1700

(a)v=3.8m/s combired velocity after impact
:confused: I can't follow any of that. It doesn't look like any kind of math that I recognize :smile: Where does 3.8m/s pop out of?
 

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