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 physics units and measurement: error analysis rounding off digits rounding of digits standard form

The vector sum of three forces having magnitudes $ | \overrightarrow F _1 | = 100 N $,  $ | \overrightarrow F _2 | = 80 N $ &  $ | \overrightarrow F _3 | = 60 N $ acting on a particle is zero. the angle between $ \overrightarrow F _1$  & $ \overrightarrow F _2 $ is nearly:-

  1. $ 53^0 $
  2. $ 143^0 $
  3. $ 37^0 $
  4. $ 127^0 $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since the vector sum of three forces is zero, they form a closed triangle. Using the law of cosines for forces F3 = 60 N, F1 = 100 N, and F2 = 80 N, we note that 60^2 + 80^2 = 100^2, meaning F1, F2, and F3 form a right-angled triangle. The angle between F1 and F2 can be found using geometry, resulting in 180 degrees minus the angle opposite to F3.

Multiple choice physics static electricity properties of charges charge properties of charge

Two charges of equal magnitude and at a distance'r' exert a force $F$ on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is

  1. $F / 8$
  2. $F / 4$
  3. $4 F$
  4. $F / 16$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Original force$,$

$F = k\dfrac{{q\,q}}{{{r^2}}}$
New force$,$
$F = k\dfrac{{\dfrac{q}{2}\,\dfrac{q}{2}}}{{{{\left( {2r} \right)}^2}}} = \dfrac{1}{{16}}F = \dfrac{F}{{16}}$
Hence,
option $(D)$ is correct answer. 

Multiple choice physics behaviour of perfect gas and kinetic theory of gases degree of freedom: law of equipartition of energy law of equipartition of energy law of equipartition of energy and mean free path

An ant is moving on a plane horizontal surface. The number of degrees of freedom of the ant will be

  1. 1

  2. 2

  3. 3

  4. 6
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Degrees of freedom represent the number of independent coordinates required to specify the position of an object. An ant on a 2D plane requires two coordinates (x, y).

Multiple choice physics behaviour of perfect gas and kinetic theory of gases degree of freedom: law of equipartition of energy law of equipartition of energy law of equipartition of energy and mean free path

A man is climbing up a spiral type staircase. His degrees of freedom are :

  1. 1

  2. 2

  3. 3

  4. more than 3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There will be three degrees of freedom. Two are along x-direction and y-directions due to translation and the last degree of freedom due to angular rotation as the  man climbs up.

Hence, Option C is correct.

Multiple choice physics behaviour of perfect gas and kinetic theory of gases degree of freedom: law of equipartition of energy law of equipartition of energy law of equipartition of energy and mean free path

An ant is walking on the horizontal surface. The number of degree of freedom of ant will be

  1. $1$
  2. $2$
  3. $3$
  4. $6$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An ant walking on a horizontal surface is constrained to move in a 2D plane (x and y coordinates). However, if the ant is considered a rigid body capable of rotation about its center of mass, it possesses 3 degrees of freedom (2 translational and 1 rotational).

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

The resultant of all the forces acting on the body in static equilibrium should be equal to 

  1. One

  2. Zero

  3. Two

  4. More than one
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The resultant of all the forces acting the body should be equal to zero. The resultant moment of all the forces acting on the body about the point of rotation should be zero.

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

The resultant moment of all the forces acting on the body about the point of rotation should be

  1. Greater than one

  2. Smaller than one

  3. Zero

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

The resultant moment of all the forces acting on the body about the point of rotation should be zero, i.e., the sum of the anticlockwise moments about the axis of rotation must be equal to the sum of the clockwise moments about the same axis.

Multiple choice rotational equilibrium option b: engineering physics motion of system of particles and rigid bodies equilibrium physics

A rope ladder with a length $\ell$ carrying a man ofmass $m$ at its end is attached to the basket ofballoon with a mass $\mathrm { M }$ . The entire system is in equilibrium in the air. As the man climbs up theladder into the balloon, the balloon descends bya height h. Then the potential energy of the man: 

  1. Increases by mg $( \ell - h )$

  2. Increases by mge

  3. Increases by mgh
  4. Increases by mg $( 2 \ell - h )$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

A body is acted upon by a constant force directed towards a fixed point. The magnitude of the force varies inversely as the square of the distance from the fixed point then path can be described by an equation similar to:

  1. $y=mx+c$
  2. ${ x }^{ 2 }+{ y }^{ 2 }={ r }^{ 2 }$
  3. $y=c{ x }^{ 2 }$

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The force field is similar to gravitational field.
So, the path is parabolic or elliptical or hyperbolic.
The exact trajectory will depend on the masses and  energy of the particle.
Option(A) is equation of a straight line, it is ruled out.
Option(B) is equation for a circle and is also eqn of an ellipse with length of major axis equal to minor axis.
Option(C) is eqn of a parabola.
Hence, (D) is the best option.

Multiple choice physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

The fours basic forces in nature are.
I. Gravitational force
II. Electromagnetic force
III. Strong nuclear force
IV. Weak nuclear force
The relative magnitudes of these forces are in the order of.

  1. III $>$ II $>$ I $>$ IV
  2. III $>$ II $>$ IV $>$ I
  3. I $>$ II $>$ III $>$ IV
  4. III $>$ I $>$ II $>$ IV
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Actually the order of the four basic forces in nature in order of their relative magnitudes are strong nuclear force $>$ Electromagnetic force $>$ Weak nuclear force $>$ Gravitational force.
Multiple choice

The work done by a force is equal to the:

  1. Force applied multiplied by the distance moved in the direction of the force

  2. Force applied multiplied by the distance moved perpendicular to the force

  3. Force applied multiplied by the time the force is applied
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Work is a scalar quantity that measures the energy transferred to or from an object by a force. It is calculated as the dot product of the force vector and the displacement vector, which is the distance moved in the direction of the force.

Multiple choice

The work done by a force on an object is equal to the product of the force and the displacement of the object in the direction of the force. The equation for work is:

  1. W = Fd

  2. W = F/t

  3. W = kx
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The work done by a force on an object is equal to the product of the force and the displacement of the object in the direction of the force. The equation for work is W = Fd, where W is the work done, F is the force, and d is the displacement of the object.

Multiple choice

A ladder 10 feet long leans against a wall. If the base of the ladder is 6 feet from the wall, how high up the wall does the ladder reach?

  1. 4 feet

  2. 6 feet

  3. 8 feet

  4. 10 feet
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The ladder, the wall, and the ground form a right triangle. The length of the ladder is the hypotenuse of this triangle. The distance from the base of the ladder to the wall is the adjacent side. The height of the ladder up the wall is the opposite side. Using the Pythagorean theorem, we can find the height of the ladder: √(10^2 - 6^2) = 8 feet.

Multiple choice

A ladder 12 feet long leans against a wall. If the base of the ladder is 4 feet from the wall, how high up the wall does the ladder reach?

  1. 6 feet

  2. 8 feet

  3. 10 feet

  4. 12 feet
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The ladder, the wall, and the ground form a right triangle. The length of the ladder is the hypotenuse of this triangle. The distance from the base of the ladder to the wall is the adjacent side. The height of the ladder up the wall is the opposite side. Using the Pythagorean theorem, we can find the height of the ladder: √(12^2 - 4^2) = 10 feet.