Question

Iguazu Falls on the border between Brazil and Argentina is 82 m high. What is the kinetic energy of a kilogram of water just before it hits the bottom of the falls. Assume the water is moving very slowly at the top of the falls.

Answer 1

Answer:

K = 803.6 J

Explanation:

• Assuming that the water is moving very slowly at the top of the falls, we can treat to the mass of water as dropping from the top.
• So, all the energy at that point is just gravitational potential energy.
• Assuming no friction during the fall, total mechanical energy must be conserved, as follows:
• ΔK + ΔU = 0 (1)
• $\Delta K = K_{f} - K_{i} = \frac{1}{2}*m*v_{f} ^{2}$
• $\Delta U = U_{f} - U_{i}$
• Taking the bottom of the falls as our zero reference level for the gravitational potential energy, we get, Uf =0.
• From (1), we get:
• ΔK = -ΔU
• ⇒ ΔK  = - (0 -m*g*h) = m*g*h
• ⇒ ΔK = 1 kg*9.8 m/s2*82 m = 803.6 J
• Kf = 803.6 J