Tag: introduction to simple machines

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Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

In a lifting machine, the efforts required for lifting loads of $20$ N and $30$ N were $5$ N and $6$ N respectively. If the velocity ratio of the machine is $20$, determine efficiencies corresponding to loads of $20 $ N and $30$ N

  1. 25 % and 20%

  2. 35% and 55%

  3. 30% and 50%

  4. 60% and 65%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let us take first case,


 in which $load=20N , effort =5N ,VR=20$

$Efficiency=\dfrac{load}{VR*effort}*100$

Putting above values, we get

$Efficiency=\dfrac{20}{20*5}*100=20%$

In second case we have.  $load=30N , efoort =6N ,VR=20$

$Efficiency=\dfrac{load}{VR*effort}*100$

Putting values we get,

$Efficiency=\dfrac{30}{20*6}*100=25%$

Hence$ Efficiency=25%,20%$

Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

If a machine overcomes a load $L$ and the distance travelled by the load is $L _d$. Similarly, the effort applied in the machine is $E$ and the distance travelled by effort is $E _d$, and $'T'$ is the time taken then velocity ratio can be written as 

  1. $\dfrac{E _d}{L _d}$

  2. $\dfrac{L _d}{E _d}$

  3. $\dfrac{E _d}{\sqrt{L _d}}$

  4. $\dfrac{\sqrt{L _d}}{E _d}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The VR is define as ratio of distance travelled by effort:distance travelled by load


$VR=\dfrac{{E}{} _{d}}{{L}{} _{d}}$

option A is correct.

Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

In a lifting machine, an effort of 500 N is to be moved by a distance of 20 m to raise a load of 10,000 N by a distance of 0.8 m. Determine the velocity ratio and mechanical advantage.

  1. 25 and 20

  2. 23 and 22

  3. 20 and 30

  4. 25 and 35
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Distance moved by effort is 20m,that of load is 0.8m

$VR=\dfrac{{E}{} _{d}}{{L}{} _{d}}$

$VR=\dfrac{20}{0.8}$

$VR=25$

the load is 10,000N and effort=500N

$MA=\dfrac{{load}{} _{d}}{{effort}{} _{d}}$

$MA=\dfrac{10000}{500}$

$MA=20$
Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

In a lifting machine, an effort of 500 N is to be moved by a distance of 20 m to raise a load of 10,000 N by a distance of 0.8 m. Determine the effort lost in friction

  1. 100 N

  2. 120 N

  3. 80 N

  4. 0 N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Work input = 500 N * 20 m = 10,000 J. Work output = 10,000 N * 0.8 m = 8,000 J. Work lost to friction = 10,000 - 8,000 = 2,000 J. Effort lost = 2,000 J / 20 m = 100 N.

Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

Efficiency of a machine can also be written as 

  1. $\dfrac{\text{velocity ratio}}{\text{mechanical advantage}} \times 100 $ %

  2. $\dfrac{\text{mechanical advantage}}{\text{velocity ratio}} \times 100 $ %

  3. $\dfrac{\text{mechanical advantage}}{\text{velocity of the gear}} \times 100 $ %

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$effiency=\eta=\dfrac{Machanical-advantage}{velocity-ratio}*100$

Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

Fill in the blank.
In the first order of lever, velocity ratio is usually __than 1 but could be __ or equal to 1

  1. greater, less

  2. less, more

  3. greater, more

  4. less, less
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a first-class lever, the fulcrum position can be adjusted. If the effort arm is longer than the load arm, the mechanical advantage (and velocity ratio) is greater than 1; if shorter, it is less than 1; if equal, it is 1.