Final answer:
You can raise or lower the load with the forks when using a forklift or similar lifting device by manipulating hydraulic pressure through the control lever.
Step-by-step explanation:
In physics, you can raise or lower the load with the forks when using a forklift or a similar lifting device. This is possible due to the application of simple machines, specifically levers and hydraulic systems.
When you move the control lever to raise the load, hydraulic fluid is pumped into the lift cylinder. This causes the piston to move upward, pushing the forks up and lifting the load. Conversely, moving the control lever to lower the load allows the hydraulic fluid to flow back into the reservoir, decreasing the pressure and allowing the load to descend.
In summary, the ability to raise or lower a load with the forks is a result of the manipulation of hydraulic pressure through the control lever of a forklift or similar equipment.