At noon, you are running to get to class and notice a friend 100 feet west of you, also running to class. If you are running south at a constant rate of 450 ft/min (approximately 5 mph) and your friend is running north at a constant rate of 350 ft/min (approximately 4 mph), how fast is the distance between you and your friend changing at 12:02 pm?

Respuesta :

Answer:

Step-by-step explanation:

Velocity of first Person [tex] v_1=450 ft/min[/tex]

Velocity of second Person [tex]v_2=350 ft/min[/tex]

Distance between them P=100 ft

Let x be the distance moved by 1 st and y be the distance moved by second person by the time 12:02 PM

In Triangle ABC

[tex]BC=350 t+450 t[/tex]

[tex]BC=800 t [/tex]

using Pythagoras

[tex]AC^2=AB^2+BC^2[/tex]

[tex]AC^2=100^2+(800t)^2[/tex]

differentiating with respect to time

[tex]2\times AC\times \frac{\mathrm{d} AC}{\mathrm{d} t}=2\times (800t)\times 800[/tex]

[tex]\frac{\mathrm{d} AC}{\mathrm{d} t}=\frac{800^2\times t}{AC}[/tex]

AC after 2 minute

[tex]AC=1603.121 ft[/tex]

[tex]\frac{\mathrm{d} AC}{\mathrm{d} t}=\frac{800^2\times 2}{1603.121}[/tex]

[tex]\frac{\mathrm{d} AC}{\mathrm{d} t}=\frac{64\times 10^4\times 2}{1603.121}[/tex]

[tex]\frac{\mathrm{d} AC}{\mathrm{d} t}=798.44 ft/min[/tex]      

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