21. Draw diagrams to illustrate the positions of
fulcrum, load and effort, in each of the following:
(a) a see-saw
(b) a beam balance
(c) a nut cracker (d) a pair of forceps
22. How can you increase the mechanical advantage
of a lever?
23. How does the friction at the fulcrum affect the
mechanical advantage of a lever?
24. State three differences between the three classes
of levers.
25. What is a pulley ?
26. What is the mechanical advantage of an ideal
pulley ?
27. The mechanical advantage of an actual pulley is
less than 1. Give a reason. What is the justification
for using the pulley then ?
28. Draw a neat labelled diagram showing a pulley
being used to lift a load. How are load and effort
related in an ideal situation ?
29. What is an inclined plane ? What is its mechanical
advantage ? Give two examples where it is used.
30. What is a screw ? Give two examples.
31. What is wheel and axle ? Give two examples.
32. How does a wheel help in moving the axle ?
33. What is a wedge? Give two examples.
Answers
Answer:
21st answer is in the photo
Explanation:
22) The mechanical advantage of a lever can be increased by increasing the effort arm or reducing the load arm.
23) How does the friction at the fulcrum affect the mechanical advantage of the lever? Solution: Friction at the fulcrum reduces the mechanical advantage.
24) The difference between the three classes depends on where the force is, where the fulcrum is and where the load is. In a first class lever, the fulcrum is located between the input force and output force. In a second class lever, the output force is between the fulcrum and the input force. write the class of lever.
25) a wheel with a grooved rim around which a cord passes, which acts to change the direction of a force applied to the cord and is used to raise heavy weights.
26) Mechanical Advantage of Pulleys
In a pulley, the ideal mechanical advantage is equal to the number of rope segments pulling up on the object. The more rope segments that are helping to do the lifting work, the less force that is needed for the job.
27) The reason for using the pulley when its mechanical advantage is equal to 1 or less than 1 is that the pulley allows us to apply the effort downwards i.e.. in a convenient direction. ... But with the help of a pulley, the effort can be applied in the downward direction to move the load upwards.
29) The mechanical advantage of an inclined plane is the ratio of the length of the plank to the vertical height of the load raised. ... Steeper the inclined plane, greater will be the effort required to push up the load. Sloping ramps, flyovers, roads on hills and staircases are a few examples of inclined planes.
30) Some examples of the uses of a screw are in a jar lid, a drill, a bolt, a light bulb, faucets, bottle caps and ball point pens. Circular stairways are also a form of a screw. Another use of the screw is in a device known as a screw pump.
31) Some examples of the wheel and axle include a door knob, a screwdriver, an egg beater, a water wheel, the steering wheel of an automobile, and the crank used to raise a bucket of water from a well. When the wheel in a wheel and axle machine is turned, so is the axle, and vice versa.
32) The axle is a cylindrical rod fixed to the centre of a circular disc-like object called the wheel. ... In a riding bicycle, when we apply force on the wheel by the pedal, the fixed axle rotates with it easily. This force that turns the axle produces a much larger movement of the wheel.
33)A wedge is a simple machine with two inclined planes put together forming a sharpened edge. Examples of wedge: knife, axe and chisel.
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