1Write the differences between a pulley and a wheel and axle.
2Write the differences between VR and MA.
3Write the differences between a jack screw and an axe.
4Write the differences between output work and input work.
5Give a reason: winding roads are built to climb hills.
6Give a reason: a crane is called a complex machine.
7Give a reason: no machine has an efficiency of 100 percent.
8Give a reason: the mechanical advantage of a real machine is less than its velocity ratio.
9Give a reason: the wheel and axle is called a continuous lever.
10What is a simple machine? Write its advantages.
11What is a complex machine? Explain with an example.
12Explain the inclined plane with examples.
13What is a wedge? Write its importance with examples.
14What is a screw? For what tasks is the screw used in daily life?
15Introduce the types of pulley with figures.
16How are the mechanical advantage and velocity ratio of a screw and a wedge found? Explain with figures.
17How can the mechanical advantage and velocity ratio of an inclined plane be increased? Write with an example.
18What is meant by saying that the efficiency of a machine is 75%?
19Why is a perfect machine practically impossible in daily life? Explain with reasons.
20How is the velocity ratio of a wheel and axle found? Explain with a figure.
21Write which simple machines combine to make the following complex machines: a sewing machine, a stitching machine, a bicycle and a flour grinding mill.
22A 90 kg object is pulled up an inclined plane 20 m long and 5 m high with a force of 300 N. Calculate the mechanical advantage, the velocity ratio and the efficiency.
23A four pulley system has an efficiency of 80%. How much force is needed to lift a 1000 N load, what is the mechanical advantage, and what are the input work and output work when the load is raised 6 m?
24The radii of a wheel and its axle are 20 cm and 5 cm. If a force of 250 N is needed to lift 500 N with it, find the mechanical advantage, the velocity ratio and the efficiency.
25A wedge used to split a wooden log has a width of 6 cm and a depth of 12 cm. If applying 300 N of force on the wedge produces a resistance of 500 N, calculate its mechanical advantage, velocity ratio and efficiency.
26A machine gives 1500 J of output work for 2000 J of input work. What is its efficiency, and where did the wasted energy go?