The negative value of work done by a conservative internal force on a system is equal to:
- AChange in total energy
- BChange in kinetic energy
- ✓Change in potential energy
- DNone of the above
Answer: C.
View full solution →Question types
PART - 1 CH - 5Work, Energy and Power question types
139 questions across 9 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.
139
Questions
9
Question groups
5
Question types
01
M.C.Q (1 Marks)
18 Q→02Fill In The Blanks[1 Marks ]
10 Q→03True False[1 Marks ]
9 Q→041 Marks Question
40 Q→052 Marks Questions
27 Q→063 Marks Question
12 Q→074 Marks Question
4 Q→08Match the following.
2 Q→095 Marks Questions
17 Q→Sample Questions
PART - 1 CH - 5Work, Energy and Power questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
If $\overrightarrow{ F }=(20 \hat{i}+15 \hat{j}-5 \hat{k})$ and $\overrightarrow{ v }=(6 \hat{i}-4 \hat{j}+3 \hat{k}) m / s$ then the instantaneous power will be :
- A35 W
- B25 W
- C90 W
- ✓45 W
Answer: D.
View full solution →The force constants of two springs are $k _1$ and $k _2$. The same strain $x$ is produced in them. If their elastic energies are $E_1$ and $E_2$. The ratio of $E_1$ and $E_2$ will be :
- ✓$\frac{k_1}{k_2}$
- B$\frac{k_2}{k_1}$
- C$\sqrt{\frac{k_2}{k_1}}$
- DNone of these.
Answer: A.
View full solution →The equivalent of S.I. unit of power or capacity (watt) is:
- A$kg ms ^{-2}$
- B$kg m ^2 s^2$
- ✓$kg m ^2 s^3$
- D$kg m ^2$
Answer: C.
View full solution →The momentum of a particle of mass m is P. Its kinetic energy will be:
- ✓$\frac{ P ^2}{2 m}$
- B$\frac{ P ^2}{m}$
- C$P ^2 m$
- D$m P$
Answer: A.
View full solution →1 horse power = ............... Watt
The relative speed of coming closer before the collison and the relative speed of moving away after the collision will be ...............
According to Albert Einstein, energy and mass are equivalent quantities. That means E =...............
In the presence of conservative forces, mechanical energy of isolated system remains. ...............
The change in kinetic energy of a body is the work done by the total force applied on it. Kf - Ki = ...............
The work done by the force is zero for a body which voluntarily returns to its initial position in such a closed path.
According to geometry, $B \cos \theta$ is the projection of vector $\overrightarrow{ B }$ onto vector A
View full solution →For simple linear or one-dimensional elastic collision,$u_1-u_2=-\left(v_2-v_1\right)$
View full solution →If the velocity of an object is doubled. Its kinetic energy will also be doubled.
The work done doesn't depend on initial speed of the body.![]()
How much should the speed of an object be increased so that its kinetic energy remains half of the initial kinetic energy?
In a gravitiaonal field, the total mechanical energy of a freely falling object increases. In this statement true or false?
When there is a collision between a negatively charged object and a positively charged object then what type of collision occurs?
Can an object have energy without momentum?
Can the scalar product of vectors be negative?
A body is initially at rest. It undergoes one-dimensional motion with constant acceleration. The power delivered to it at time t is proportional to :
(a) $t^{1 / 2}$
(b) $t$
(c) $t^{3 / 2}$
(d) $t^2$.
View full solution →(a) $t^{1 / 2}$
(b) $t$
(c) $t^{3 / 2}$
(d) $t^2$.
Answer carefully, with reasons :
(a) In an elastic collision of two billiard balls, is the total kinetic energy conserved during the short time of collision of the balls (i.e. when they are in contact) ?
(b) Is the total linear momentum conserved during the short time of an elastic collision of two balls?
(c) What are the answers to (a) and (b) for an inelastic collision?
(d) If the potential energy of two billiard balls depends only on the separation distance between their centres, is the collision elastic or inelastic? (Note, we are talking here of potential energy corresponding to the force during collision, not gravitational potential energy).
(a) In an elastic collision of two billiard balls, is the total kinetic energy conserved during the short time of collision of the balls (i.e. when they are in contact) ?
(b) Is the total linear momentum conserved during the short time of an elastic collision of two balls?
(c) What are the answers to (a) and (b) for an inelastic collision?
(d) If the potential energy of two billiard balls depends only on the separation distance between their centres, is the collision elastic or inelastic? (Note, we are talking here of potential energy corresponding to the force during collision, not gravitational potential energy).
State if each of the following statements is true or false. Give reasons for your answer.
(a) In an elastic collision of two bodies, the momentum and energy of each body is conserved.
(b) Total energy of a system is always conserved, no matter what internal and external forces on the body
are present.
(c) Work done in the motion of a body over a closed loop is zero for every force in nature.
(d) In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system.
(a) In an elastic collision of two bodies, the momentum and energy of each body is conserved.
(b) Total energy of a system is always conserved, no matter what internal and external forces on the body
are present.
(c) Work done in the motion of a body over a closed loop is zero for every force in nature.
(d) In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system.
A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5m each time. Assume that the potential energy lost each time she lowers the mass is dissipated. (a) How much work does she do against the gravitational force? (b) Fat supplies 3.8 × 107J of energy per kilogram which is converted to mechanical energy with a 20% efficiency rate. How much fat will the dieter use up?
A body of mass 0.5 kg travels in a straight line with velocity $v=a x^{3 / 2}$ where $a=5 m^{-1 / 2} s^{-1}$. What is the work done by the net force during its displacement from $x=0$ to $x=2 m$ ?
View full solution →Underline the correct alternative :
(a) When a conservative force does positive owrk on a body, the potential energy of the body increases/decreases/remains unaltered.
(b) Work done by a body against friction always results in a loss of its kinetic/potential energy.
(c) The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces on the system.
(d) In an inelastic collision of two bodies, the quantities which do not change after the collision are the total kinetic energy/total linear momentum/total energy of the system of two bodies
(a) When a conservative force does positive owrk on a body, the potential energy of the body increases/decreases/remains unaltered.
(b) Work done by a body against friction always results in a loss of its kinetic/potential energy.
(c) The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces on the system.
(d) In an inelastic collision of two bodies, the quantities which do not change after the collision are the total kinetic energy/total linear momentum/total energy of the system of two bodies
The potential energy function for a particle executing linear simple harmonic motion is given by $V(x)=k x^2 / 2$, where $k$ is the force constant of the oscillator. For $k=0.5 Nm ^{-1}$, the graph of $V (x)$ versus $x$ is shown in Fig. Show that a particle of total energy 1 J moving under this potential must 'turn back' when it reaches $x= \pm 2 m$.
View full solution →A family uses 8 kW of power. (a) Direct solar energy is incident on the horizontal surface at an average rate of 200W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW? (b) Compare this area to that of the roof of a typical house.
The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1.5 m, what is the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance?
Two identical ball bearings in contact witheach other and resting on a frictionless table are hit head-on by another ball bearing of the same mass moving initially with a speed V. If the collision is elastic, which of the following (Fig.) is a possible result after collision?
Answer the following :
(a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained? The rocket or the atmosphere?
(b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. Yet the work done by the gravitational force over every complete orbit of the comet is zero. Why?
(c) An artificial satellite orbiting the earth in very thin atmosphere loses its energy gradually due to dissipation against atmospheric resistance, however small. Why then does its speed increase progressively as it comes closer and closer to the earth?
(d) In Fig. (i) the man walks 2m carrying a mass of 15 kg on his hands. In Fig. (ii), he walks the same distance pulling the rope behind him. The rope goes over a pulley, and a mass of 15 kg hangs at its other end. In wich case is the work done greater?
(a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained? The rocket or the atmosphere?
(b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. Yet the work done by the gravitational force over every complete orbit of the comet is zero. Why?
(c) An artificial satellite orbiting the earth in very thin atmosphere loses its energy gradually due to dissipation against atmospheric resistance, however small. Why then does its speed increase progressively as it comes closer and closer to the earth?
(d) In Fig. (i) the man walks 2m carrying a mass of 15 kg on his hands. In Fig. (ii), he walks the same distance pulling the rope behind him. The rope goes over a pulley, and a mass of 15 kg hangs at its other end. In wich case is the work done greater?
A body of mass 2 kg initially at rest moves under the action of an applied horizontal force of 7N on a table with coefficient of kinetic friction = 0.1. Compute the
(a) work done by the applied force in 10 s,
(b) work done by friction in 10 s,
(c) work done by the net force on the body in 10 s,
(d) change in kinetic energy of the body in 10 s, and interpret your results.
(a) work done by the applied force in 10 s,
(b) work done by friction in 10 s,
(c) work done by the net force on the body in 10 s,
(d) change in kinetic energy of the body in 10 s, and interpret your results.
A pump on the ground floor of a building can pump up water to fill a tank of volume $30 m^3$ in 15 min . If the tank is 40 m above the ground, and the efficiency of the pump is $30 \%$, how much electric power is consumed by the pump ?
View full solution →An electron and a proton are detected in a cosmic ray experiment, the first with kinetic energy 10 keV, and the second with 100 keV. Which is faster, the electron or the proton ? Obtain the ratio of their speeds. (electron mass =$9.11 \times 10^{-31} kg$, proton mass $\left.=1.67 \times 10^{-27} kg, 1 eV =1.60 \times 10^{-19} J\right)$.
View full solution →| Column - A | Column – B |
| 1. $\hat{i} \cdot \hat{j}=\hat{j} \cdot \hat{k}=\hat{k} \cdot \hat{i}=$ | (A) 1 |
| 2. $|\hat{i}|=|\hat{j}|=|\hat{k}|$ | (B) Proportional |
| 3. $(3 \hat{i}+4 \hat{j}-5 \hat{k})$. $(5 \hat{i}+4 \hat{j}+3 \hat{k})=$ | (C) 0(ZERO) |
| 4. Work done by the force acting perpendicular to the displacement is always | (D) 16 |
| 5. Work done (w) and heat generated (H) on a system are mutual | (E) Zero |
| Column - A | Column – B |
| 1. Friction forces and viscous forces are | (A) Electrical energy |
| 2. The value of mathematical equaivalent of heat is | (B) $\frac{1}{2} I \omega^2$ |
| 3. Transformation of chemical energy takes place in a dry cell | (C) Non-conservative force |
| 4. The value of rotational kinetic energy of the body is | (D) Newton/meter |
| 5. The unit of spring constant 1S | (E) 4.2 J/calorie |
A rain drop of radius 2 mm falls from a height of 500m above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) untill at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey? What is the work done by the resistive force in the entire journey if its speed on reaching the grounds is $10 ms^{-1} ?$
View full solution →Prove that after a direct elastic collision between two balls of equal mass, their velocities mutually interchange.
If an object of mass $M$ moving with velocity $\mu$ has a direct elastic collision with an other stable object of mass $m$ then prove that the energy loss of the object of mass $M$ and the result of its intial energy will be $\frac{4 m M }{( M +m)^2}$
View full solution →What is the law of conservation of mechnical energy? Prove that mechanical energy is conserved in a freely falling object. Or Write the law of conservation of mechanical energy. Prove that the mechanical energy of a freely falling object is conserved. Make labelled diagram.
Two objects of masses $m_1$ and $m_2$ are moving with velocities $u_1$ and $u_2$ respectively collide in an inelastic collision. If after the collision both the objects move together then calculate the change in the value of energy
View full solution →Generate a PART - 1 CH - 5Work, Energy and Power paper free
Pick question groups from the list above, set marks and difficulty, and export a branded PDF with step-by-step answer keys. First 3 chapters free — no signup.