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**1. Homework Statement**

I've calculated the time, the distance, the height of the counterweight before launch, the mass/weight, and I need to calculate the energy efficiency.

How to go about it?

h = 0.71 m

m = 1.445 kg

g = 9.8 m/s^2

t = 0.7 s

x = 4.44 m

**2. Homework Equations**

Eg = mgh

Vix = x/t

y = Viy(t) + (1/2) a(t)^2

Ek = (mv^2)/2

**3. The Attempt at a Solution**

THEORETICAL YIELD:

h = 0.71 m

m = 1.445 kg

g = 9.8 m/s^2

Eg = mgh

= (1.445 kg)(9.8 m/s2)(0.71 m)

= 10.05 J

ACTUAL YIELD:

t = 0.7 s

x = 4.44 m

Vix = x/t

= (4.44 m)/(0.7 s)

= 6.34 m/s

y = Viy(t) + (1/2) a(t)^2

0.71 m = Viy(0.7 s) + (1/2) (-9.8 m/s2)(0.7 s)^2

Viy = 4.44 m/s

Vi^2 = (Vx)^2 + (Viy)^2

Vi^ = (6.34 m/s)^2 + (4.44 m/s)^2

Vi= 7.74 m/s

Ek = (1/2) mv^2

= (1/2) (1.445 kg)(7.74 m/s)^2

= 43.28 J

43.28 J / 10.05 J = 430%

I don't think my trebuchet is 430% efficient.

What did I do wrong?

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