What effort force is required to raise a load W using a screw jack with helix angle a and friction angle <j)__________________?
Show answer Hide answer
Answer: A. Wtan(a + )
Explanation
Lifting a load with a screw jack requires overcoming both the mechanical load and thread friction forces. Resolving forces inclined at the helix angle and friction angle yields the standard tangent summation formula. The required effort force is directly proportional to the total load multiplied by the tangent of alpha plus phi. A screw jack converts rotational effort into linear lifting motion using an inclined plane wrapped around a cylinder. The helix angle represents the steepness of the screw thread, while the friction angle represents surface resistance. Friction in power screws significantly affects mechanical advantage and overall operating efficiency.
Automotive jacks use this mechanical principle to lift heavy vehicles with minimal manual effort. Machine vises and clamping devices rely on power screws to generate high holding forces securely. Engineers select appropriate thread angles to ensure self-locking behavior and prevent load slipping. Option B represents the formula used for lowering a load rather than raising it against gravity. Options C and D use incorrect trigonometric functions that do not satisfy the inclined plane force equilibrium. others
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. How is rupture stress defined________________?
Show answer Hide answer
Answer: D. load at breaking point/neck area
Rupture stress calculation requires dividing the final applied load at the breaking point by the minimum necked cross-sectional area. As ductile tension specimens elongate, localized necking drastically reduces the cross...
Q2. How is the tensile strength of a material calculated using test data_________________?
Show answer Hide answer
Answer: B. original cross-sectional area
Conventional tensile strength is calculated by dividing maximum load by original cross-sectional area. Engineering stress uses initial gauge dimensions rather than changing areas during the test. This standard method pro...
Q3. Under what loading conditions is the material property of resilience taken into account_________________?
Show answer Hide answer
Answer: D. shock loading
Resilience is the capacity of a material to absorb energy when deformed elastically, which is crucial under shock loading conditions. High resilience allows components to store kinetic impact energy temporarily without s...
Q4. What internal factor dictates the elastic properties of various engineering materials___________________?
Show answer Hide answer
Answer: D. stress at elastic limit
The elastic limit marks the maximum stress threshold up to which a material deforms elastically and dictates its fundamental behavior. Internal atomic bonds stretch and recover completely when applied stresses remain str...
Q5. The circumferential force in a cylinder wall sets up a stress perpendicular to the longitudinal axis, commonly referred to as___________________?
Show answer Hide answer
Answer: B. hoop stress
Circumferential stress set up in a cylinder wall perpendicular to the axis is called hoop stress. Internal fluid pressure pushes outward in all radial directions, creating this tensile hoop stress. Hoop stress represents...
Q6. What designation is given to materials that exhibit identical elastic characteristics in all orientations______________?
Show answer Hide answer
Answer: C. isotropic
Materials that exhibit identical elastic properties in all directions are termed isotropic. Isotropic materials have uniform directional characteristics, meaning their elastic modulus and Poisson ratio remain constant ev...