Chimney climber, Newton's lawquestion

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In summary, the minimum force the climber must exert to remain in contact with the wall is 490.5N. This is calculated by finding the total upward force needed, which is equal to the weight of the climber, and dividing it by the sum of the static coefficients of friction between his shoes and back and the wall. This ensures that the climber is supported by both friction forces and does not fall.
  • #1
hemetite
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Hi, i just need to see whether my answer is logically correct?

A 70kg climber is supported in the chimney by the friction forces exerted on his shoes and back. The static coefficients of frictions between his shoes and the wall, and between his back and the wall, are 0.80 and 0.60 respectively. What is the minimum force he must exert? Assume the walls are vertical and that friction forces are both at maximum...

Here is my answer.

For the climber to remain in contact with the wall.

Both Frictional Force(shoe) and Frictinal Force(back) = mg = 70*9.81

else he will fall...

Fn1= the force he must exert by his shoe
Fn2= the force he must exert by his back

therefore

Frictional Force(shoe)= 0.80 * Fn1

mg=0.80*Fn1

Fn1(shoe)=853.4N

Frictional Force(back) = 0.60* Fn2
mg=0.6*Fn2
Fn2(back)=1144.5N.

Therefore minimum normal force he must exert to satisfy both...= 1144.5N

Logical and correct?
 
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  • #2
Why must he support his total weight with his feet and support his total weight with his back? Do you see where Newton's Law comes in? The force he exerts on the walls of the chimney with his feet and back are equal.
 
  • #3
I knew both force need to be equal

you are saying that i should dived the mg into 2...

50% load handle by the shoe

50% load handle by his back..?
 
  • #4
hemetite said:
For the climber to remain in contact with the wall.

Both Frictional Force(shoe) and Frictinal Force(back) = mg = 70*9.81
No. As Halls' already explained, don't set each individual friction force equal to the weight. Instead, the total upward force must equal his weight.
else he will fall...

Fn1= the force he must exert by his shoe
Fn2= the force he must exert by his back
How are these forces related? Hint: Analyze the horizontal forces acting on the climber.
hemetite said:
I knew both force need to be equal

you are saying that i should dived the mg into 2...

50% load handle by the shoe

50% load handle by his back..?
No. Don't make any assumptions about the friction forces being equal.
 
  • #5
Okay..then it should be like this

Fn=exertion force

0.80*Fn + 0.6*Fn = mg

Fn = (70*9.81) / (0.80+0.60) = 686.7 / 1.4 = 490.5N

correct?
 
  • #6
Looks good.
 
  • #7
thanks.. :)
 

Related to Chimney climber, Newton's lawquestion

What is a chimney climber and what does it have to do with Newton's law?

A chimney climber is a toy or game that involves a small figure climbing a rope or string by repeatedly flipping over. It is related to Newton's law of motion because the toy relies on the principle of action and reaction, where each flip of the figure creates a force that propels it upwards.

How does Newton's first law of motion apply to the chimney climber?

Newton's first law, also known as the law of inertia, states that an object at rest will remain at rest unless acted upon by an external force. In the case of the chimney climber, the figure remains at rest until a force (the flip) is applied, causing it to move.

What is the role of gravity in the chimney climber and Newton's law?

Gravity is the force that pulls objects towards the center of the Earth. In the chimney climber, gravity is the force that brings the figure back down after each flip. This force is also described by Newton's law of universal gravitation.

Can you explain how Newton's third law of motion is demonstrated in the chimney climber?

Newton's third law states that for every action, there is an equal and opposite reaction. In the case of the chimney climber, each flip of the figure creates a force that pushes it upwards. This force is then met with an equal and opposite force from the string, causing the figure to flip back down.

Are there any real-life applications of the chimney climber and Newton's law?

The chimney climber and Newton's law have been used to study and understand various physical phenomena, such as the motion of satellites and planetary orbits. The principle of action and reaction is also applied in various mechanical devices, such as rockets and jet engines.

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