Machine

1. The efficiency of a machine is always less than 100% because the (a) load lifted is always greater than the effort applied (b) effort applied is always greater than the load lifted (c) velocity ratio is always greater than the mechanical advantage (c) work output is always greater than the work input
Right Choice: Option C

2. Which of the following statements defines correctly the efficiency of a machine? (a) the load carried by the machine divided by effort required in carrying the load. (b) the distance moved by the load divided by the distance moved by the effort. (c) the useful work done by the machine divided by the total work put into it. (d) the movement of the load divided by the movement of the effort about the same point.
Right Choice: Option C

3. Which of the following machines does NOT apply the lever principles? (a) claw hammer (b) wheelbarrow (c) single moving pulley (d) sugar tongs
Right Choice: Option B

4. The areas of the effort and load pistons of a hydraulic press are 0.5m2 and 5m2 respectively. If a force F] of 100N is applied on the effort piston, the force F2 on the load is (a) 10N (b) 100N (c) 500N (d) 1000N
Right Choice: Option D

5. The mechanical advantage (MA) of an inclined plane depends on (a) its length (b) its height (c) the product of its length and height (d) the ratio of its length to its height.
Right Choice: Option D

EXERCISE

6. A 20 – toothed gear wheel drives a 60 – toothed one. If the angular speed of the smaller wheel is 120 rev s’1 the angular speed of the larger wheel is (a) 3 revs-1 (b) 40 revs-1 (c) 360 revs-1 (d) 2400 revs-1

7. The pitch of a screw jack is 0.45cm and the mechanical advantage d the arm is 60cm long If the efficiency of the jack is 75/π%, calculate the mechanical advantage (a) 400 (b) 300 (c) 200 (d) 150

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