1:A load of 800N is raised using a screw jack whose lever arm is 49cm has a pitch of 2.5cm.If it is 40% efficient,find the velocity ratio and mechanical advantage
2:A screw has a pitch of 3.5mm. The effort is applied using a handle which is 44cm long.Calculate the velocity ratio.
1. The velocity ratio is equal to the distance moved by the effort (lever arm) divided by the distance moved by the load (pitch).
Distance moved by effort = 49cm
Distance moved by load = pitch = 2.5cm
Velocity ratio = 49cm / 2.5cm = 19.6
The efficiency is given as 40%, so the mechanical advantage is:
Mechanical advantage = (load / effort) / efficiency
Effort = load / mechanical advantage * efficiency
Mechanical advantage = (800N / effort) / 0.4
Effort = 800N / (mechanical advantage * 0.4)
Substituting the known values:
Mechanical advantage = (800N / effort) / 0.4
19.6 = (800N / effort) / 0.4
7.84 = 800N / effort
Effort = 800N / 7.84
Effort = 102.04N
The mechanical advantage is then:
Mechanical advantage = load / effort
Mechanical advantage = 800N / 102.04N
Mechanical advantage = 7.84
Therefore, the velocity ratio is 19.6 and the mechanical advantage is 7.84.
2. The velocity ratio is equal to the distance moved by the effort (handle) divided by the distance moved by the load (pitch).
Distance moved by effort = handle length = 44cm
Distance moved by load = pitch = 3.5mm = 0.35cm
Velocity ratio = 44cm / 0.35cm = 125.7
Therefore, the velocity ratio is 125.7.