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

The mechanical advantage for a pulley system is determined by

  1. counting the number of strands holding the resistance force.

  2. counting the number of strands holding and not holding the resistance force.

  3. adding the radii of the pulleys.

  4. multiplying the radii of the pulleys.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an ideal pulley system, the mechanical advantage is equal to the number of segments or strands of rope actively supporting the resistance force (load). Counting these strands gives the direct multiplier for the input force.

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.