Solving Friction Question: Child on Stair Rail w/ 40 Degree Angle

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SUMMARY

The problem involves a child of mass 25 kg sliding down a frictionless stair rail inclined at a 40-degree angle. The correct acceleration is calculated using the equation f=ma, leading to an acceleration of 7.1 m/s², not the previously calculated 4.9 m/s². The error arose from misapplying the sine function for the angle, which should be sin(40) instead of sin(30). The final speed at the bottom after sliding 4.0 m can be determined using kinematic equations.

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  • Basic trigonometry, specifically sine functions
  • Concept of frictionless surfaces in physics
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Homework Statement



A child sits on a freshly oiled, straight stair rail that is frictionless. She has a mass of 25 kg and the rail makes a 40 degree angle with the ground. IF she slides 4.0 m before reaching the bottom, what is her speed there?

Homework Equations



f=ma

The Attempt at a Solution



I did .1(9.8)(sin30)
then i set it equal to .1a=.1(9.8)sin30
and got 4.9 m/s/s but the actual answer is 7.1 m/s/s?
where did i go wrong?
 
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Firstly, if it is frictionless then it is not a friction problem lol. What other equation do you think you need to solve this?
 

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