Retarding force impacting a stationary object

  • Thread starter JamesTheEng
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In summary: What happened to the deceleration you were calculating?It looks like the initial velocity of the pile and driving weight is 0. The combined mass is 1350 kg, so the average velocity will be (150kg/1350kg)(3.8m/s)= 0.422m/s.You appear to be using 1700 in your equations but I don't see where that comes from either.The resistance is the force applied by the ground to stop the pile and driving weight. That force is 1350 kg times the deceleration. You have calculated the deceleration but have not used it.
  • #1
JamesTheEng
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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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  • #2
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?
 

FAQ: Retarding force impacting a stationary object

What is a retarding force?

A retarding force is a force that opposes the motion of an object. It acts in the opposite direction of the object's motion and can slow down or stop the object's movement.

How does a retarding force impact a stationary object?

A retarding force can cause a stationary object to remain at rest, or if the object is already in motion, it can slow down or eventually stop the object's movement.

What are some examples of retarding forces?

Some examples of retarding forces include friction, air resistance, and drag. These forces can occur when an object moves against a surface, through a fluid, or in a medium such as air.

How does the magnitude of a retarding force affect the motion of the object?

The greater the magnitude of the retarding force, the greater its impact on the object's motion. This means that a larger retarding force will cause a greater slowdown or stoppage of the object's movement.

Can a retarding force ever be beneficial?

Yes, a retarding force can be beneficial in certain situations. For example, the retarding force of friction allows us to walk without slipping and helps cars come to a stop. In some cases, retarding forces can also be harnessed for energy production, such as in wind turbines and brakes on vehicles.

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