Physics

Forces, Energy and Machines

281 Questions

Forces, energy, and machines are fundamental physics concepts focusing on mechanics, work, power, and simple machines. These topics regularly appear in general science sections of competitive exams. Use these questions to practice calculating resultant forces, mechanical advantage, and work done in various scenarios.

Resultant force calculationsMechanical advantage of leversWork and power equationsApparent weight in elevatorsBending moments

Forces, Energy and Machines Questions

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

A pulley system of VR of 2 and efficiency of 50%. If the effort moves through a distance of 5m. Calculate the distance moved by the load.

  1. 2m

  2. 5.6m

  3. 10m

  4. 2.5m
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Given:  $VR=2$


From the relation $VR=\dfrac{\text{Distance moved by effort}}{\text{distance moved by load}}$


Using formula we get distance moved by the load is $2.5m$

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

Akhil has to lift a load of $800N$ onto a platform of $2m$ height. Instead, he pushes the load up a ramp $4m$ long. Find the force required to lift the load vertically up.

  1. $200N$
  2. $600N$
  3. $400N$
  4. $800N$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The vertical force is the gravitational force means weight of the load. 

According to question, the weight of load is $mg=800 N$, this will be the required force to lift the load vertically.  

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 $10000$ N by a distance of $0.8$ m. Determine the velocity ratio and mechanical advantage?

  1. 10 and 35

  2. 20 and 35

  3. 10 and 25

  4. 25 and 20
Reveal answer Fill a bubble to check yourself
D 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 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

It is easier to draw up a wooden block along an inclined plane than to haul it vertically, principally because:

  1. the friction is reduced

  2. the mass becomes smaller

  3. only a part of the weight has to be overcome
  4. $g$ becomes smaller
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The vertical plane $W=mgh$
for inclined plane $W'=mghsin(Q)$
$sinQ<1$
$W>W'$
hence only one part of weight is to overcome

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

Akhil has to lift a load of 800 N onto a platform of 2 m height. Instead, he pushes the load up a ramp 4 m long. Find the force required to roll the load up the ramp.

  1. 200 N

  2. 600 N

  3. 400 N

  4. 800 N
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Force required to roll the load up the ramp (F) $=\displaystyle \frac{load \times height}{distance}$
$= 800 \displaystyle \times \frac{2}{4} = 400 N$

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

Akhil has to lift a load of 800 N onto a platform of 2 m height. Instead, he pushes the load up a ramp 4 m long. Find the work done by Akhil in lifting the load vertically up.

  1. 800 J

  2. 1600 J

  3. 400 J

  4. 200 J
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The work done by Akhil in lifting the load vertically up $=$ Force $\times$ height
$= 800 \times 2 = 1600 \ J$

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

A nut can be opened by a lever of length $0.25$ m by applying a force of $80$ N. What should be the length of the lever if a force of $32$ N is enough to open the nut?

  1. $625$ m
  2. $1625$ m
  3. $0.625$ m
  4. $6.25$ m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the principle of moments: F1 * L1 = F2 * L2. 80 N * 0.25 m = 32 N * L2. L2 = (80 * 0.25) / 32 = 20 / 32 = 0.625 m.

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

A man of mass $80kg$ carrying a load of $20kg$ walks up a stair case in $20s$. If the number of steps is $40$ and width and height of each step are $20cm$ and $15cm$ respectively. The efficiency of the man is

  1. $20 \%$
  2. $25\%$
  3. $40\%$
  4. $50\%$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total mass = 100 kg. Total height = 40 * 0.15 m = 6 m. Work done = mgh = 100 * 10 * 6 = 6000 J. Power output = 6000 / 20 = 300 W. Assuming human efficiency is related to power, this question is ambiguous without a defined input power.

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

A man uses a crowbar of length $1.5m$ to raise a load of $75kgf$ by putting a sharp edge below the bar at a distance $1m$ from his hand. Calculate the mechanical advantage. 

  1. $0$
  2. $1$
  3. $2$
  4. $4$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Load $ = 75 kgf$
Length of crowbar $= 1.5 m$
Effort arm $= 1 m $
So, Load Arm $= \text{Length of crowbar - Effort arm}$


$\Rightarrow 1.5 - 1 = 0.5 m$
Mechanical Advantage $= \dfrac{\text{Effort Arm}}{\text{Load Arm}} = \dfrac{1}{0.5} =2$

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

A man uses a crowbar of length $1.5m$ to raise a load of $75kgf$ by putting a sharp edge below the bar at a distance $1m$ from his hand. Calculate the effort needed.

  1. $75kgf$
  2. $375kgf$
  3. $37.5 gf$
  4. $37.5kgf$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Load $ = 75 kgf$
Length of crowbar $= 1.5 m$
Effort arm $= 1 m $
So, Load Arm $= \text{Length of crowbar - Effort arm}$
$\Rightarrow 1.5 - 1 = 0.5 m$
Mechanical Advantage $= \dfrac{\text{Effort Arm}}{\text{Load Arm}} = \dfrac{1}{0.5} =2$


Effort needed $= \dfrac{\text{Load}}{\text{Mechanical Advantage}} = \dfrac{75}{2} = 37.5 kgf$