STUDY LESSON:-21 [CIVIL ENGINEERING]
For Competitive exams/Railway jobs/Semester exam/Self Study Purpose
1. Efficiency of a screw jack can be expressed as _________2. The efficiency of screw jack is maximum when __________
3. A machine will be self locking if its efficiency comes less than _________
4. What will be the kinetic energy if the momentum of its body is doubled?
5. If an elevator weighs 10,000 kgf which is pulled in upward direction by a wire with 4m/s velocity in 2 second with uniform acceleration.. what will the tension in cable pulling the elevator?
6. The angle of reaction of roller support and the base should be _________
7. what will happen to the earths weight if it stops rotate?
8. Walking on Ice is slippery because _________
9. What will be the escape velocity of earth if its mass and radius are doubled?
10. ___________ causes weightlessness while orbiting the earth in space.
Answers:-
1. tanα/tan(α+Φ) [α= Helix angle and Φ-Angle friction)
2. α=45°-(Φ/2)
3. 50%
4. It will increased by 4 times
5. 8000 kgf [T=W(1-(a/g))]
6. 90°
7. Increase
8. Increase of pressure causes it to melt
9. Remain unchanged
10. Zero gravity
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