A weight of 1000 N can be lifted by an effort of 80 N. If the velocity ratio is 20, the machine is

Answer: Option A

Understanding the Question:
Imagine a simple machine like a pulley system. It helps you lift heavy objects with less effort.
We have a weight (load) of 1000 N that needs to be lifted.
We only need to apply an effort of 80 N to lift it.
The velocity ratio (VR) is 20. This tells us how much the machine multiplies the effort. A VR of 20 means the effort moves 20 times the distance the load moves.

Mechanical Advantage (MA):
The machine's mechanical advantage (MA) shows how much it multiplies the effort.
We calculate MA by dividing the load by the effort: MA = Load / Effort = 1000 N / 80 N = 12.5

Efficiency:
Efficiency tells us how effective the machine is. It's the ratio of MA to VR:
Efficiency = (MA / VR) * 100% = (12.5 / 20) * 100% = 62.5%

Reversible vs. Non-reversible Machines:
A reversible machine has an efficiency greater than 50%. It can work in the reverse direction without extra help. For example, it can both lift a weight and lower it smoothly.
A non-reversible machine has an efficiency less than 50%. To reverse it (lower the weight), you might need to apply an external force.

Answer:
Since the efficiency (62.5%) is greater than 50%, the machine is reversible. The correct option is A.