A circus clown is fired from a cannon into a net....

Clifford

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Nov 15, 2006
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A circus clown is fired from a cannon into a net that is situated 2.0 m above the cannon at some distance from it. The cannon is elevated at 50 degrees to the horionztal and the clown's speed at lunch if 15 m/s.
(a) Find the horizontal distance from the cannon where the net needs to be placed in order for the clown to land in it.
(b) Calculate the clown's velocity as he lands in the net

(a) To calculate the horizontal velcoity you do 15cos50 = 9.642 m/s
for the vertical velocity you do 15sin50 = 11.491 m/s

dv = vv1t + 1/2gt^2
-2 = 11.491t - 4.9t^2
4.9t^2 - 11.491t - 2 = 0
by using the quadratic formula you get
t = 6.345 s

subing the time into d = vt
d = 9.642(6.345)
d = 61.178 metres

(b) vv2^2 = vv1^2 + 2gdv
vv2^2 = 11.491^2 + 2(-9.8)(2)
vv2 = -9.6

v2^2 = vv1^2 + vv2^2
v2 = 15.3

tan theta = 9.6 / 9.642
theta = 45

the clowns velocity has he hits the net is 15.3 m/s [36 degrees E of S]

I am pretty sure I did part a right but I am not sure about part b.
 
I'm having a problem with your quadratic formula, notation and signs but...
You are using
h = h<sub>0</sub>+v<sub>0</sub>t-.5gt<sup>2</sup>
Since everything is referenced to the cannon mouth, h<sub>0</sub> = 0 and
h=-4.9t<sup>2</sup> + 11.491t
The height of the net is h=2 (I am using up is positive) so apply the quadratic formula to
2=-4.9t<sup>2</sup> + 11.491t or
4.9t<sup>2</sup> - 11.491t + 2 = 0 (Note the sign change on the 2 from yours.)
I get roughly t = 2.15 and .189 for the zeros (Where the height above the cannon mouth is 2 m)

The method looks good from there on.
 
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