NAIJA EXAM RUNZ ONLINE PHYSICS TUTORIAL : TOPIC: MACHINE
MACHINES
Definition:
A machine is any device which makes energy to be used for the performance of work in a convenience way. In machines, small effort is required to carry a large load.
Examples of a simple machines are; levers, inclined plane, screw jack, wheel and axle, gear wheel, hydraulic press e.t.c.
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1. Effort: This is the point where you applied force on machine. It is measure in Newton 'N' and represented by E.
2. Load: This is force on the machine. It is measure in Newton and rep. by L
3. Mechanical Advantage/Disadvantage: Mechanical Advantage 'M.A' is defined as the ratio of load to effort when the value is greater than 1 i.e the load is larger than effort.
It is called Mechanical Disadvantage when it value is less than 1 i.e the effort is larger than the load. It has no unit since both the load and effort are both measured in Newton 'N'.
Mathematically;
M.A=Load/Effort= L/E.
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4, Velocity Ratio (V.R): This is the ratio of effort distance to load distance. It also has no unit since numerator and denominator are measure in metre 'm'.
Mathematically;
V.R= effort distance/load distance=x/y
5. Efficiency 'Eff.': This is the ratio of M.A to V.R expressed in percentage. It unit is %.
Mathematically;
Eff.= M.A×100/V.R.
Also it is given as;
Eff.=Work output×100/Work input
Note:
Since Work=force ×distance.
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Work output = Load Work= Load×distance moved by load.
Workinput= Effort Work= effort ×distance moved by effort. Work is measure in joule.
Types of Machines
1. Lever: Lever is sub divided into three which are;
a. First Class Lever: This is a machine in which Fulcrum is in between the load and effort. Examples of such are; table spoon, hammer, e.t.c.
b. Second Class Lever: This is when the load is in between the effort and fulcrum. Examples are; wheel Barrow, but cracker e.t.c
c. Third Class Lever: This is when the effort is in between the load and fulcrum. Examples are, water pale, fore arm e.t.c.
VELOCITY RATIO AND ITS APPLICATIONS IN MACHINES
2. Inclined plane: This is inform of right angle triangle. The hypotenuse is the effort distance and the height is the load distance in inclined plane.
V.R= effort distance/ load distance.
In case when only the angle (tita '®') is given we have;
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V.R=1/sin®.
3. Screw Jack:
V.R= 2πa/p
Where; a= jack handle distance.
p= Pitch of the jack.
4. Pulley:
V.R is equal to the number of pulley in a machine. If we have 5 pulleys in a machine that means the velocity ratio is 5.
5. Wheel and Axle, and Gear wheel:
V.R= larger wheel radiu /small wheel radius. That is, V.R=R/r.
CALCULATIONS:
1. An effort of 50N is applied to lift a load of 100N with the aid of a simple machine. Calculate the mechanical advantage.
Solution:
Given that, E=50N, L=100N, M.A=?
Recall that,
M.A = L/E = 100/50
Therefore, M.A = 2.
2. A labourer raises a load of mass 120kg by using a system of 6 pulleys. He exerts a force of 400N on the rope. Calculate the efficiency of the machine.
Solution:
Given that, L=120kg=120×10=1200N,
V.R=6 (no of pulleys),
Force applied i.e Effort 'E'=400N,
Eff=?
Apply,
Eff. =M.A×100/V.R
But M.A is not given in the equation so we need to find it. How can we do these?
From, M.A=L/E= 1200/400
M.A= 3.
Recall;
Eff. =M.A×100/V.R
Eff.= 3×100/6
Eff.= 300/6
Eff.= 50%.
NOTE: TO CONVERT MASS 'KG' TO NEWTON 'N', YOU MULTIPLY THE MASS BY 10.
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Exercise:
The velocity ratio and efficiency of a system of pulley are 6 and 80% respectively. How much effort is required to lift a load of mass 120kg with this system? (SSCE)
END OF LECTURE..
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Definition:
A machine is any device which makes energy to be used for the performance of work in a convenience way. In machines, small effort is required to carry a large load.
Examples of a simple machines are; levers, inclined plane, screw jack, wheel and axle, gear wheel, hydraulic press e.t.c.
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Terms Used In Machines1. Effort: This is the point where you applied force on machine. It is measure in Newton 'N' and represented by E.
2. Load: This is force on the machine. It is measure in Newton and rep. by L
3. Mechanical Advantage/Disadvantage: Mechanical Advantage 'M.A' is defined as the ratio of load to effort when the value is greater than 1 i.e the load is larger than effort.
It is called Mechanical Disadvantage when it value is less than 1 i.e the effort is larger than the load. It has no unit since both the load and effort are both measured in Newton 'N'.
Mathematically;
M.A=Load/Effort= L/E.
(www.naijaexamrunz.blogspot.com)
4, Velocity Ratio (V.R): This is the ratio of effort distance to load distance. It also has no unit since numerator and denominator are measure in metre 'm'.
Mathematically;
V.R= effort distance/load distance=x/y
5. Efficiency 'Eff.': This is the ratio of M.A to V.R expressed in percentage. It unit is %.
Mathematically;
Eff.= M.A×100/V.R.
Also it is given as;
Eff.=Work output×100/Work input
Note:
Since Work=force ×distance.
(www.naijaexamrunz.blogspot.com)
Work output = Load Work= Load×distance moved by load.
Workinput= Effort Work= effort ×distance moved by effort. Work is measure in joule.
Types of Machines
1. Lever: Lever is sub divided into three which are;
a. First Class Lever: This is a machine in which Fulcrum is in between the load and effort. Examples of such are; table spoon, hammer, e.t.c.
b. Second Class Lever: This is when the load is in between the effort and fulcrum. Examples are; wheel Barrow, but cracker e.t.c
c. Third Class Lever: This is when the effort is in between the load and fulcrum. Examples are, water pale, fore arm e.t.c.
VELOCITY RATIO AND ITS APPLICATIONS IN MACHINES
2. Inclined plane: This is inform of right angle triangle. The hypotenuse is the effort distance and the height is the load distance in inclined plane.
V.R= effort distance/ load distance.
In case when only the angle (tita '®') is given we have;
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V.R=1/sin®.
3. Screw Jack:
V.R= 2πa/p
Where; a= jack handle distance.
p= Pitch of the jack.
4. Pulley:
V.R is equal to the number of pulley in a machine. If we have 5 pulleys in a machine that means the velocity ratio is 5.
5. Wheel and Axle, and Gear wheel:
V.R= larger wheel radiu /small wheel radius. That is, V.R=R/r.
CALCULATIONS:
1. An effort of 50N is applied to lift a load of 100N with the aid of a simple machine. Calculate the mechanical advantage.
Solution:
Given that, E=50N, L=100N, M.A=?
Recall that,
M.A = L/E = 100/50
Therefore, M.A = 2.
2. A labourer raises a load of mass 120kg by using a system of 6 pulleys. He exerts a force of 400N on the rope. Calculate the efficiency of the machine.
Solution:
Given that, L=120kg=120×10=1200N,
V.R=6 (no of pulleys),
Force applied i.e Effort 'E'=400N,
Eff=?
Apply,
Eff. =M.A×100/V.R
But M.A is not given in the equation so we need to find it. How can we do these?
From, M.A=L/E= 1200/400
M.A= 3.
Recall;
Eff. =M.A×100/V.R
Eff.= 3×100/6
Eff.= 300/6
Eff.= 50%.
NOTE: TO CONVERT MASS 'KG' TO NEWTON 'N', YOU MULTIPLY THE MASS BY 10.
(www.naijaexamrunz.blogspot.com)
Exercise:
The velocity ratio and efficiency of a system of pulley are 6 and 80% respectively. How much effort is required to lift a load of mass 120kg with this system? (SSCE)
END OF LECTURE..
IS THIS HELPFUL?
Tell us if you find this helpful.
Thanks for this
ReplyDeleteNicely summarised