Properties of a machine Machines 1 Machines Next Slide Properties of a machine Transfer energy from one place to another place Change the direction of a force Change the magnitude of a force Can never change the magnitude of energy Examples Diagram

Terms related to a machine Machines 2 Machines Next Slide Terms related to a machine Effort (the force we apply to the machine) Load (the force that the machine supplies to move the desired object Input energy = work done by the effort = effort  distance moved by the effort Output energy = work done on the load = load  distance moved on the load

Terms related to a machine Machines 3 Machines Next Slide Terms related to a machine Calculation Since output energy is always smaller than input energy, the efficiency is always smaller than 100 %. Loss energy may become sound and internal energy due to friction or be used to increase the P.E. the movable part of the machine.

Various kinds of machine Different Machines 1 Machines Next Slide Various kinds of machine A machine which enables a heavy load to be raised by a small effort, is a force multiplier.. Various kinds of lever : nut cracker, scissors, single-wheel cart Diagram Inclined plane Calculation Wheel-and-axle Calculation

Various kinds of machine Different Machines 2 Machines Next Slide Various kinds of machine Screw-jack Calculation Hydraulic press Calculation Single pulley Calculation Gears Bicycle Calculation

END of Machine

Machines 1 Machines Next Slide Transfer energy from one place to another energy Change the direction of a force tension upwards pulling force downwards

Back to Machines 1 Machines Click Back to Change the magnitude of a force heavy load small effort

Machines 3 Machines Next Slide By making use of a lever, an effort 20 N is used to raise a block (mass 5 kg) by 5 cm as shown in the following diagram. What is the efficiency of this lever? How much energy has been lost? 20 N mass : 5 kg 5 m 1 m pivot

Machines 3 Machines Next Slide effort 1 m pivot 5 m 0.25 m 0.05 m

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Different Machines 1 Machines Next Slide Nut Cracker load effort pivot Scissors effort load pivot paper

Back to Different Machines 1 Machines Click Back to Single-wheel cart load effort pivot sand

Different Machines 1 Machines Next Slide A block (mass 20 kg) is pulled by a force 100 N upwards along the incline plane shown. Find the efficiency of the machine and the friction acting on the block by the plane. 5 m 2 m rough incline plane 100 N

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Different Machines 1 Machines Next Slide 2 kg of water is raised in a bucket with mass 0.5 kg by a wheel-and-axle machine as shown in the following figure. Assume that the handle has been turned by an effort 10 N for one round, find its efficiency. 0.3 m 0.1 m 10 N water 2 kg bucket 0.5 kg

Back to Different Machines 1 Machines Click Back to In this case, only the water is considered as the load. The bucket is thought as one part of the machine. Therefore, when we consider the energy gained by the load, we only consider the P.E. gained of the water.

Different Machines 2 Machines Next Slide A screw jack is used to raise the load (mass : 1000 kg) by an effort 50 N as shown in the following figure. The height of the pitch is 1 mm and the length of the handle is 0.5 m. Find its efficiency. Such an machine needs a LOW efficiency, why? Load :1000 kg 0.5 m height of pitch : 1 mm Effort : 50 N

Back to Different Machines 2 Machines Click Back to Assume that the handle has been turned for one round. The load would be raised by a height equal to the height of pitch. Small efficiency means the energy lost due to friction is large. Therefore, the friction of this machine is very large. If we remove the effort, the friction is large enough to prevent the load from falling downwards.

Different Machines 2 Machines Next Slide A hydraulic press is used to move a load (mass : 100 kg) upwards for 1 cm as shown. The distance pushed by the effort 20 N is equal to 1 m (Why?). Find its efficiency. oil 1 m 1 cm effort 20 N load 100 kg

Back to Different Machines 2 Machines Click Back to It is very difficult to compress oil. Therefore, the volume of oil transferred to the column with the load remains the same.

Different Machines 2 Machines Next Slide A fixed pulley is used to move an load 20 kg upwards by an effort 250 N. The load has been raised by a height 1 m. Find its efficiency. load : 20 kg effort : 250 N

Back to Different Machines 2 Machines Click Back to The tension in the string holding the load is not equal to 250 N. It was because there is friction between and the string and the pulley.

Different Machines 2 Machines Next Slide A bicycle has the following dimensions: Find the distance moved by pedal and the wheel respectively if the crank has been turned for one round. Do you think that this machine is a force multiplier? 0.50 m 0.25 m 18 teeth 36 teeth

Back to Different Machines 2 Machines Click Back to In this case, the distance moved by the effort (pedal) is much shorter than the load (bicycle). Therefore, it is not a force multiplier. Bicycle is a machine that cannot save force. However, it can greatly increase the distance moved.