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Grade 9Mechanics

A helicopter is ascending vertically with a speed of 8.0mper sec. AT a height of the 12m above earth. Apackage dropped from window. How much time does it take for package to reach the ground

Profile image of surendra surendra
7 Years agoGrade 9
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1 Answer

Profile image of Arun
7 Years ago
write the equation of motion of the package: 

y(t)=y0+v0t+1/2 at^2 

y(t) is the height of the object at any time, t 
y0,v0 are initial height and speed 
a is acceleration 

here: 

y0=12 m 
v0=+8 m/s/s since the package has, initially, the motion of the helicopter 

a = g =-9;8m/s/s, be careful to use signs properly, if we call up the positive direction (as we did in setting v0=+8 m/s), then g must be negative 

we want to find the time for the package to hit the ground, that is, the time when y(t)=0 

0=12+8 t-4.9t^2 

this is a quadratic in t, You can solve it

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