The top of a 10-ft ladder is leaning against a wall, and the base of the ladder is on the ground. If the top of the ladder slides down the wall at a rate of 2 ft/sec, how fast (in ft/sec) is the bottom of the ladder moving along the ground when the bottom of the ladder is 5 ft from the wall?

Respuesta :

Answer:

Ladder is moving away from the wall with the speed of 3.464 ft/s

Step-by-step explanation:

Consider the figure attached

Given that top of ladder slides down with the speed of 2ft/sec, i.e

[tex]\frac{dh}{dt}=2fts^{-1}[/tex]

Length of ladder =10 ft

bottom of the ladder is 5 ft from the wall i.e b=5

By pythagorous theorem

[tex]h^2+b^2=100---(1)\\\\h^2=100-(5)^2\\\\h^2=75\\\\h=5\sqrt{3}ft[/tex]

Differentiating equation (1) w.r.to t

[tex]2h\frac{dh}{dt}+2b\frac{db}{dt}=\\\\2(5)\frac{db}{dt}=-2(5\sqrt{3})(2)\\\\\frac{db}{dt}=-2\sqrt{3}\\\\\frac{db}{dt}=-3.464\,ft/s[/tex]

Negative sign shows that ladder is moving away from wall

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