Physics

Forces, Energy and Machines

267 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

The apparent weight of a man in a lift is less than his real weight

  1. when the lift is going down with uniform acceleration

  2. when the lift is going up with uniform acceleration

  3. when the lift is stationary

  4. at no time
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a lift accelerates downward, the normal force exerted by the floor on the person is less than their weight, making them feel lighter (apparent weight is less than real weight).

Multiple choice

Some villagers were carrying heavy pots on their heads. Many of them complained that their heads ached badly due to the weight. A clever person among them suggested that they should remove their shirts, roll it and place it on their heads like a ring to carry the heavy pots. When this was done, the weight on their heads seemed easier to carry. What is the correct explanation for this?

  1. They got some rest while rolling their shirts.

  2. By doing this the weight of the pots decreased.

  3. The weight would be equally distributed along the ring of the rolled up cloth.

  4. Since, the position of pots were a bit elevated, the pressure was reduced.

  5. Wind speed decreased the pressure of the weight.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The weight will be equally distributed along the ring, i.e. it will be distributed along a wider area than being concentrated at a single point on the head. Thus, the pressure decreases.

Multiple choice friction laws of motion physics

A lineman of mass 60 kg is holding a vertical pole. The coefficient of static friction between his hands and the pole is 0.5.If the able to climb up the pole,Then the minimum force with which he should press the pole with his hands $ [g = 10 ms^{-2}] is $

  1. 1200 N

  2. 600 N

  3. 300 N

  4. 150 N
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice friction laws of motion physics

A light ladder is supported on a rough floor and lens against a smooth wall, touching the wall at height 'h' above the floor. A man climbs up the ladder until the base of the ladder is on the verge of slipping. The coefficient of statice friction between the foot of the ladder and the floort is $\mu$. The horizontal distance moved by the man is

  1. $\mu^2h$
  2. $\mu/h$
  3. $\mu h$
  4. $\mu^2h^2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is a standard mechanics problem involving the equilibrium of a ladder. The horizontal distance x is related to the height h and coefficient of friction mu by the condition of slipping at the base.

Multiple choice physics motion and measurement guidelines for writing the units conventions for the use of si units rules to write name and symbol for units of s.i. system

The correct way to represent an unit amount of force is :

  1. 1 newton

  2. 1 Newton

  3. 1 NEWTON

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The full name of the unit, irrespective of the fact whether it is named after a scientist or not, is always written with the lower initial letter. Hence 1 newton is correct way to write.

Multiple choice surface tension physics surface energy of a liquid work done in stretching a liquid surface: surface energy of a liquid properties of matter

A square frame of length $L$ is immersed in soap solution and taken out. The force experienced by the square plate is

  1. $TL$
  2. $2TL$
  3. $4TL$
  4. $8TL$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As force applied by tension will be from outer side and from inner side as well.

Total length $L' = 2(4L) = 8L$
So  $F = L'T =  8TL$

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

A force acts on a $30$gm particle in such a way that the position of the particle as a function of time is given by $x=3t-4t^2+t^3$, where x is in metres and t is in seconds. The work done during the first $4$ second is?

  1. $2.88$J
  2. $450$mJ
  3. $490$mJ
  4. $530$mJ
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$M=20gm=0.020kg$

$x=3t-4t²+t³m$
$v=dx/dt=3-8t+3t²m/s$
$a=dv/dt=-8+6tm/s²$
$Force=ma=0.120t-0.160N$
$Workdone=dW=Fdx=F\ast \frac { dx }{ dt } \ast dt=(0.120t-0.160)\ast (3-8t+3t²)dt=0.360t³-1.440t²+1.640t-0.480$
$W=0.090t⁴-0.490t³+0.82t²-0.480t=2.88J$