Final answer:
The calculated mechanical advantage is 1.5, rounded to 2. The effort required to lift a 120N load with this pulley system is 60N. The work done is 30J, and the energy wasted due to 75% efficiency is about 7.5J.
Step-by-step explanation:
The student's question asks for the mechanical advantage of a pulley system given a velocity ratio and efficiency, along with the effort required to lift a load, the work done by the effort, and the energy wasted. Using the formula for mechanical advantage (MA) in the context of efficiency (Eff) and velocity ratio (VR), we use the relationship MA = Eff * VR. With an efficiency of 75% (or 0.75) and a velocity ratio of 2, we calculate MA as 0.75 * 2 = 1.5. However, since MA must be a whole number, we approximate it to the nearest whole number as 2, which will affect subsequent calculations.
The effort (E) required to lift a load (Load) when the mechanical advantage is known used the relationship E = Load / MA. For a load of 120N and an MA of 2, we get E = 120N / 2 = 60N. The work done by the effort (W) is calculated by multiplying the force exerted by the distance moved by the force in the direction of the force, W = E * distance. So, W = 60N * 0.5m = 30J (not accounting for efficiency).
The energy wasted is calculated based on the efficiency. Since only 75% of the work input is used for lifting, there is a 25% loss. The work input is the work done by the effort which we calculated as 30J.