Related Rates: Shadow Problem with Moving Object

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SUMMARY

The discussion centers on a related rates problem involving a spotlight, a wall, and a moving man casting a shadow. The man, who is 2 meters tall, walks towards a wall located 12 meters away at a speed of 1.6 m/s. The goal is to determine how fast the length of his shadow on the wall is decreasing when he is 4 meters from the wall. The solution requires establishing a relationship between the distances involved using similar triangles.

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  • Knowledge of similar triangles and their properties
  • Familiarity with basic differentiation techniques
  • Ability to set up and solve equations involving rates of change
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Homework Statement


A spotlight on theground shines on a wall 12 m away. If a man 2m tall walks from the spotlight toward the building at a speed of 1.6m/s. how fast is the length of his shadow on the building decreasing when he is 4m from the building?

The Attempt at a Solution



x=4m dx/dt=1.6m/s dy/dt=?

I am kinda of stuck on this one. I know that as x decreases z and y will also decrease. But I am really not to sure how to proceed on this one any hints?
 
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You need a relation between x, the distance from the wall and y, the height of the shadow. Draw a picture and find two similar triangles.
 
Last edited:

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