Work, Energy And Power - Class 11 Medical Physics - Extra Questions

The potential energy (in SI units) of a particle of mass 2 kg in a conservative field is U = 6x - 8y. If the initial velocity of the particles is $$\vec{u} = -1.5 \hat{i} + 2\hat{j}$$, then find the total distance travelled by the particle in the first two seconds.



Give one example to illustrate that heat can be generated from the energy of motion.



Which energy is cause for glowing of bulb in electrolytic cell?



Pick the odd one out from the following based on the nature of energy possessed by them. (moving car, water stored in a tank, a book on a table, ceiling fan in OFF position)



Give some important forms of energy.



State the energy changes in the following case while in use.
A ceiling fan.



State the energy changes in the following case while in use.
An electric iron.



What energy transformation takes places just before the flower pot reaches the ground ?
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You ride a bicycle. In what sense is your bicycle solar=powered?



An open box slides across a frictionless, icy surface of a frozen lake. What happens to the speed of the box as water from a rain shower fall vertically downward into the box? Explain.



State the energy changes in the following devices while in use:
(i) A loud speaker
(ii) A glowing electric bulb



What is the Frictional Energy ? What role does it play in the total mechanical energy of a body ?



Fill the blanks with the correct option:
position   potential   mechanical    chemical   light   kinetic.
1.An electric fan converts electrical energy into________energy.
2.Coking gas converts______energy into heat energy.
3.The energy possessed by a spring is______energy.
4.The energy possessed by a body due to its______is called potential energy.
5.The energy possessed by a body due to its motion is called______energy.



State whether the energy possessed in the following is kinetic or potential; compressed spring, stretched bow, moving arrow, water stored in a dam, a stone at the top of a building, bird resting on the branch of a tree.



If a battery is used to charge a capacitor, work done by the battery is $$W$$ and energy stored in the capacitor is $$E$$. How these two are related ?



Each Voyager spacecraft was accelerated towards escape speed from the Sun by gravitational force exerted by Jupiter on the spacecraft. Does the interaction of the spacecraft with Jupiter meet the definition of an elastic collision?



Find the maximum and minimum distances between the bars during the subsequent motion of the system, if the masses of the bars are equal.
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Find the maximum and minimum distances between the bars during the subsequent motion of the system, if the masses of the bars are equal to $$m_1$$ and $$m_2$$, and the force $$F$$ is applied to the bar of mass $$m_2$$.
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The assembly of two discs as shown in figure is placed on a rough horizontal surface and the front disc is given an initial angular velocity $$\omega_{0} $$ Determine the final linear and angular velocity when both the discs start rolling. It is given that friction is sufficient 10 sustain rolling in the rear wheel from the starting of motion.
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Match the column from List $$I$$ to List $$II$$



Name any five different forms of energy other than mechanical energy.



Match the entries in Column I with those in Column II correctly.



Prove work energy theorem for a constant force.



A body moves from point A and B under the action of a force, varying in magnitude as shown in figure below. Obtain the work done. Force is expressed in newton and displacement is in metre. 
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A bullet of mass $$m\ kg$$ and horizontal speed $$u\ ms^{-1}$$ strikes a block of wood of mass $$M\ kg$$ and instantly comes to rest with respect to the block. The block is suspended from the ceiling by means of thin wires. Calculate the height to which the block rises. Also, estimate the amount of heat produced in the block.



A stone is projected vertically up to reach maximum height 'h'. The ratio of its kinetic energy to potential energy , at a height $$\dfrac{4h}{5}$$ will be:



A liquid drop of $$1.00\ g$$ falls from a height of a cliff $$1.00\ km$$. It hits the ground with a speed of $$50\ ms^{-1}$$.what is the work done by the unknown resistive force.



Describe the work-energy relationship by giving a suitable example



When a bullet of mass $$10\ g$$ goes through a board of uniform density and uniform thickness of $$2.5\ cm$$ its velocity decrease from $$1\ km/s$$ to $$0.5\ km/s$$. Find the loss of $$K.E$$ of the bullet. The average resistive force does the bullet experience in passing through the board? 



Give an example for each of the following energy conversion: (1) electrical energy to kinetic energy. (2) chemical energy to electrical energy (3) sound energy to electrical energy 



A body of mass $$10 kg$$ is kept at a height of $$5 m$$. It is allowed to fall and reach the ground.
What is the total mechanical energy possessed by the body at the height of $$2 m$$ assuming it is a frictionless medium?



The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.



What are collisions? Explain the possible types of collisions. Develop the theory of one dimensional elastic collision.



A 'loop the loop' cart runs down an incline and then inside a circular track $$6 \,m$$ in diameter making a complete cycle. Neglecting friction, find the minimum height above the top of the circular track from which the cart must be released.



Describe the collision in $$1$$-D for both elastic and inelastic collision.



Derive the formula for the kinetic energy of an object of mass m, moving with velocity v.



The decrease in potential energy between top position A and bottom position B is, 
$$= m g r - ( - m g r ) = 2 m g r \quad \ldots ( 1.63 )$$ 
This must be equal to the increase in kinetic energy, when particle move from A to B 
i.e. $$\quad \frac { 1 } { 2 } m v _ { 2 } ^ { 2 } - \frac { 1 } { 2 } m v _ { 1 } ^ { 2 }$$ 



A neutron moving with a velocity of $$ 10^4 m/s $$ collides head-on with another neutron at rest. Assuming that the collision is elastic,find the velocity o each particle on separation.



In given figure, a block of ice slides down a friction less ramp at angle $$\theta = 50^0$$ while an ice worker pulls on the block (via a rope) with a force $$\overrightarrow F_r$$ that has a magnitude of $$50 \ N$$ and is directed up the ramp. As the block slides through distance $$d = 0.50 \ m$$ along the ramp, its kinetic energy increases by $$80 \ J$$. How much greater would its kinetic energy have been if the rope had not been attached to the block?
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Can you object have mechanical energy even if its momentum is zero? Explain.



Can you object have momentum even if its mechanical energy is zero? 



Two bodies of unequal mass are moving in the same direction with equal kinetic energy. The two bodies are brought to rest by applying retarding force of same magnitude. How would the distance moved by them before coming to rest compare?



Name six different forms of energy?



Is it possible that no transfer of energy may take place even when a force is applied to a body?



The bob of a simple pendulum is imparted a velocity $$5\, m\, s^{-1}$$ when it is at its mean position. To what maximum vertical height will it rise ou reaching to its extreme position if $$60$$% of its enemy is lost in overcome friction of air?



Match the column A with column B.
(A) Energy conversation(B) Instruments
(i) Electrical energy to sound energy(a) Solar cell
(ii) Electrical energy to heat energy(b) Dynamo (generators)
(iii) Mechanical energy to electrical energy(c) Electric heater
(iv) Light energy to electrical energy(d) Speaker



What is energy? Name different forms of energy. Give the unit of energy.



When we stretch a wire, why do we have to do work?



An inclined plane $$(\theta)$$ has its topmost point at a height ii. Prove that the work done to bring a mass to the ground level either vertically or along the inclined surface is equal and is $$mgh$$. Also, prove that the velocity of the mass at the lowermost point is $$\sqrt{2gh}$$.



In daily life, we use different forms of energy of various activities . List the forms of energy familiar to you 



Write down the energy change in each of the following : 
Generator
Cell
Battery
Solar cell



While the flower pot is falling down, what forms of energy does it possess?



Let the mass of the flower pot 15 kg and hight of the sunshade 4m. 
To sum up the amount of energy When on the sunshade.

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A horizontal plane supports a plank with a bar of mass $$m=1.0\:kg$$ placed on it and attached by a light elastic non-deformed cord of length $$l_0=40\;cm$$ to a point $$O$$ (figure shown above). The coefficient of friction between the bar and the plank equals $$k=0.20$$. The plank is slowly shifted to the right until the bar starts sliding over it. It occurs at the moment when the cord deviates from the vertical by an angle $$\theta=30^\circ$$. Find the work that has been performed by that moment by the friction force acting on the bar in the reference frame fixed to the plane is $$A / 100$$ JOule. Find the value of A.
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Particle 1 moving with velocity $$v=10\:m/s$$ experienced a head-on collision with a stationary particle 2 of the same mass. As a result of the collision, the kinetic energy of the system decreased by $$\eta=1.0\:\%$$. Find the magnitude of the velocity of particle 1 after the collision in m/s.



A solid spherical ball rolling without slipping collides elastically with an identical ball at rest, as shown in the figure. Assuming that the frictional forces are small enough to have negligible effect during the instant of collision, calculate, the velocity of each ball along enough time after the collision when each ball is again rolling without slipping.

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Water falling from a $$50\ m$$ high fall is to be used for generating electric energy. If $$1.8 \times 10^{5}kg$$ of water falls per hour and half the gravitational potential energy can be converted into electric energy, how many $$100\ W$$ lamps can be lit?



An ideal spring of unstreched length of 0.2m is placed horizontally on a friction less table as shown below.One end of the spring is fixed ad the other end is attached to a block of mass M= 8 kg. The 8kg vlock is also attached to a massless string that passes overa small friction less pulley. A block of mass= 4kg hangs from other end of the string.When the spring and block system in equilbrium,the length of the spring is.25m and the 4kg block is 5m above the floor.At $$t ={ t }_{ 0 }$$,string is cut at point P, then
(A)Tension in the string before $${ t }_{ 0 }$$ is 800N.
(B)Force constsnt of the spring is 800N/m.
(C)Time taken by the 4kg block to hit the floor after $$ { t }_{ 0 }$$ is 1 sec.
(D)Maximum speed achieved by 8kg block is 5m/s. 

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To simulate car accidents, auto manufactures study the collision of moving cars with mounted springs of different spring constants. Consider a typical simulation with a car of mass 1000 kg moving with a speed of 18.0 km/h on a smooth road and colliding with a horizontally mounted spring of spring constant 6.25 *10^{3} N/m. What is the maximum compression of the spring?



A particle of mass $$m$$ is kept on the top of a smooth sphere of radius $$R$$. It is given a sharp impulse which imparts it a horizontal speed $$V$$. 
(a) Find the normal force between the sphere and the particle just after the impulse. 
(b) What should be the minimum value of $$V$$ for which the particle does not slip on the sphere?  
(c)Assuming the velocity $$v$$ to be half the minimum calculate in part, 
(d) find the angle made by the radius.



Consider a moving cart of mass 120 kg with a kinetic energy K. If its velocity is doubled , how much should be mass be decreased so that the KE does not change?



A body of mass m moving with velocity v makes a head-on collision with another body of mass 2 m which is initially at rest. The loss of kinetic energy of the colliding body (mass m) is



You drop a $$2.00\, kg$$ book to a friend who stands on the ground at distance $$D = 10.0\, m$$ below. If your friends out-stretched hands are at distance $$d = 1.50\, m$$ above the ground (Fig. 8-30), (a) how much work $$W_g$$ does the gravitational force do on the book as it drops to her hands? (b) What is the change $$\Delta \,U$$ in the gravitational potential energy of the bookEarth system during the drop? If the gravitational potential energy $$U$$ of that system is taken to be zero at ground level, what is $$U$$ (c) when the book is re-leased and (d) when it reaches her hands? Now take $$U$$ to be $$100\, J$$ at ground level and again find (e) $$W_g$$,(f) $$\Delta \,U,$$ (g) $$U$$ at the release point, and (h) $$U$$ at her hands.
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Is work done while kicking a football?



A projectile of mass $$m$$ moves to the right with a speed $$c_i$$. The projectile strikes and sticks to the end of a stationary rod of mass $$M$$, length $$d$$, pivoted about a frictionless axle perpendicular to the page through $$O$$. We wish to find the frictionless change of kinetic energy of the system due to collision. 
If the angular speed of the system after the collision is $$\omega$$, what is the angular momentum of the system after the collision? 
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Figure shows a battery-operated alarm clock.
Use words from the box to complete the sentences.
chemical, electrical, kinetic, light, sound , thermal

The battery stores ............... energy. When the battery is first connected , electrical energy is transferred to ............ energy of the clock's hands. Some of the electrical energy is transferred to the surroundings as ............... energy. When the alam bell rings, electrical energy is transferred to ............ energy.
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energy is conventionally measured in Calories as well as in Joules. One Calorie in nutrition is one kilocalories, defined as $$1\ kcal=4.186\ J$$. Metabolizing $$1\ g$$ of fat can re;lease $$9.00\ kcal$$ A student decided to try to lose weight by exercising. He plans to run up and down the stairs in a football stadium as facts as he can and as many times as necessary. To evaluate the program, suppose he runs up flight of $$80$$ steps, each $$0.150\ m$$ high, in $$65.0\ s$$ For simplicity, ignore the energy he uses in coming down (which is small). Assume a typical efficiency for human muscles is $$20.0\\%$$. this statement means that when your body converts $$100 J$$ form metabolizing fat, $$20\ J$$ goes into doing mechanical work (here, climbing stairs). The reminder goes into extra internal energy. Assume the students mass is $$75.0\ kg$$ I s this activity in itself a practical way to lose weight?



A small ball moves at a constant velocity $$\nu$$ along a horizontal surface and at point $$A$$ fall is into a vertical well of depth $$H$$ and radius $$r$$. The velocity $$\nu$$ of the ball forms an angle $$\alpha$$ with the diameter of the well drawn through point $$A$$ Fig
Determine the relation between $$\nu,\ H,\ r$$ and $$\alpha$$ for which the ball can "get out" of the well after elastic impact with the walls.
Friction losses should be neglected.
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Class 11 Medical Physics Extra Questions