Tag: physics

Questions Related to physics

A boy can exert a maximum effort of $250\  N$, so he uses an inclined plane to lift the load up. What should be the minimum length of the plank used by him to lift a mass of $ 50 \ kg$ to a height of $1 \ m$ ?

physics lever common machines terms related to machines introduction to simple machines

  1. $2$ $ m $

  2. $5$ $ m $

  3. $25$ $ m$

  4. $6$ $ m$

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Correct Option: A
Explanation:

Work done  $W = mgh$
$W = 50\times 10\times 1$  $N$
$W=500 N $
$W =$ Effort $\times$ distance
Distance$=500/250= 2m$

A coolie uses a sloping wooden plank of length $2.0 m$ to push up a drum of mass $100 kg$ into the truck at a height $1.0 m$. What is the mechanical advantage of the sloping plank ?

physics lever common machines terms related to machines introduction to simple machines

  1. 6

  2. 5

  3. 2

  4. 10

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Correct Option: C
Explanation:

Length of the sloping wooden plank , $l = 2 m$
Vertical height , $h = 1 m$
We, know that for a inclined plane,
Mechanical Advantage $= \dfrac{Length \ of \ the \ incline}{vertical \ height}$
$\Rightarrow \dfrac{l}{h} = \dfrac{2}{1} = 2$

A fire tongs has its arms $20cm$ long. It is used to lift a coal of weight $1.5kgf$ by applying an effort at a distance $15cm$ from the fulcrum. Find the mechanical advantage of fire tongs.

physics lever common machines terms related to machines introduction to simple machines

  1. $3$

  2. $0.50$

  3. $0.90$

  4. $0.65$

Show answer
Correct Option: A
Explanation:

Effort Arm $ = 15 cm$
Load Arm $ = 20 - 15 = 5 cm$
Mechanical Advantage $= \dfrac{\text{Effort Arm}}{\text{Load Arm}} = \dfrac{15}{5} = 3$

A fire tongs has its arms $20 \ cm$ long. It is used to lift a coal of weight $1.5 \ kgf$ by applying an effort at a distance $15 \ cm$ from the fulcrum. Find the effort needed.

physics lever common machines terms related to machines introduction to simple machines

  1. $0.2 kgf$

  2. $1.5 kgf$

  3. $2.5 kgf$

  4. $2.0 kgf$

Show answer
Correct Option: D
Explanation:

$Load= 1.5kgf$
$Load \ arm= 20cm$
$Effort \ arm=15 cm$
$Effort \ = 20 \times 1.5/15= 2.0kgf$
The fulcrum in tongs is the joint end of the arms

It is harder to cut an apple with a butter-knife, because:

physics lever common machines terms related to machines introduction to simple machines

  1. butter-knife has more inclination

  2. mechanical advantage of a butter-knife is less

  3. it has a high angle of wedge

  4. all the above

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Correct Option: D

It is difficult to climb the steps having greater inclination. Why?

physics lever common machines terms related to machines introduction to simple machines

  1. Less erect steps require less energy

  2. Greater inclination requires less effort because of the high mechanical advantage

  3. Greater iriclination requires more effort because of the low mechanical advantage

  4. None of the above

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Correct Option: C

For a _________, the mechanical advantage is always less than one.

physics lever common machines terms related to machines introduction to simple machines

  1. first order lever

  2. second order lever

  3. third order lever

  4. both A and C

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Correct Option: C

Mechanical advantage of a second order lever is :

physics lever common machines terms related to machines introduction to simple machines

  1. always less than one

  2. less than or equal to one

  3. always greater than one

  4. greater than or equal to one

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Correct Option: C

If the threads of a screw are closer : 

physics lever common machines terms related to machines introduction to simple machines

  1. Mechanical advantage decreases

  2. Inclination increases

  3. Effort required will be less

  4. All of the above

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Correct Option: D

The force applied on the machine to overcome the load is called

physics lever common machines terms related to machines introduction to simple machines

  1. Mechanical advantage

  2. Load

  3. Effort

  4. All of the above 

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Correct Option: C
Explanation:

Definition of effort $\left( \varepsilon \right)$. The resistive or opposing force to be overcome by a machine is called the load $\left(L\right)$.