A SCREW JACK HAS 90 THREADS TO THE METRE. THE EFFORT IS APPLIED AT THE END OF AN ARM 20CM LONG . WHAT FORCE MUST BE APPLIED TO LIFT A LOAD OF 120N
To find the force that must be applied to lift a load of 120N using a screw jack, you need to understand the concept of mechanical advantage and how it applies to screw jacks.
A screw jack is a simple machine that consists of a screw (threaded rod) and a lever arm. The threads on the screw allow it to move up or down when the lever arm is rotated. The mechanical advantage of a screw jack is determined by the number of threads per unit length on the screw. In this case, you mentioned that the screw jack has 90 threads to the meter.
The mechanical advantage (MA) of a screw jack can be calculated using the following formula:
MA = Length of lever arm / Pitch of the screw
The pitch of the screw is the distance between adjacent threads, which can be calculated by dividing the total length of the screw by the number of threads. In this case, the pitch can be calculated as:
Pitch = 1 meter / 90 threads = 0.0111 meters (approximately)
Now, let's calculate the mechanical advantage:
MA = 0.2 meters / 0.0111 meters ≈ 18.02
The mechanical advantage tells us how much the force applied to the lever arm is amplified when lifting a load. In other words, the force required to lift the load is reduced by a factor equal to the mechanical advantage.
To find the force that must be applied, you can use the following equation:
Force (effort) = Load / Mechanical Advantage
Plugging in the values:
Force = 120N / 18.02 ≈ 6.659N
Therefore, to lift a load of 120N using this screw jack, you would need to apply a force of approximately 6.659N at the end of the 20cm long lever arm.