Test F.Sc Physics 1st year Chapter No.3 and 4. Long Questions

Q.No.3: - Attempt any two                               2   x  5   =  10

(i) Calculate the (a) time of flight (b) height of projectile (c) range of projectile

(ii) Derive the relation of absolute of P.E at the surface of Earth.

(iii) State and explain law of conservation of energy.

(iv) Find the final velocities of balls after an elastic collision.

Test F.Sc Physics Chapter no.3 and 4 short questions

Q.No.2: -Write the answer of the following questions.   2   x   5  =  10

(i) Prove that the units of impulse and momentum is same.

(ii) State isolated system and also describe that why is it important for law of conservation of momentum?

(iii) If two balls collide and after collision the magnitude of their velocities will remain same but their direction changes. Explain which type of collision both the balls will suffer.

(iv) Let two balls collide in such a way that their collision is perfectly elastic and both the balls are of same mass and the velocity of second ball is zero. Find the velocities of both the balls after collision?

(v) If you move with a bag in your hand and you move in the forward direction then what will be work done by your force and gravitational force? Explain it.

Test F.Sc Physics 1st year Chapter No.3 and 4. M.C.Qs

(i) The dimensions of impulse is that of

(a) Power            (b) velocity             (c) momentum            (d) acceleration

(ii) The time rate of change of momentum is called

(a) Velocity          (b) distance             (c) momentum           (d) force

(iii) The time rate of change speed is called

(a) Acceleration     (b) jerk                  (d) velocity                 (d) non of these

(iv) When we projected the ball with some velocity vi at an angle with the x-axis then the value of velocity at the highest point of its flight will be equal to its

(a) x-component    (b) y-component    (c) (d) non of these

(v) At which angle the range of projectile will be equal

(a) ϴ=45⁰ , 30⁰      (a) ϴ=30⁰ , 60⁰      (a) ϴ=60⁰, 90⁰            (d) non of these

(v) We can calculate the momentum by using

(vi) The work done will be zero if ϴ is

(a) 270⁰, 90⁰            (b) 0⁰, 180⁰            (b) 90⁰, 0⁰             (b) 0⁰, 360⁰

(vii) The work done by gravitational force is

(a) Independent of path (d) dependent of path(c) both (a) and (b).

(d) Non of these

(viii) The dimension of power is



(ix) is the dimension of

(a) Power                 (b) velocity                (c) work                  (d) K.E

(x) The absolute P.E at infinite distance will be

(a) ∞                         (b) 0                            (c) maximum            (d) non of these

Test Chapter No.13 current electricity 2nd year F.Sc Long questions

                                                                Long Questions

Q.No.3: -  Explain the following question.  Attempt all  ( Mark 3+3=6 each question)

Q.No.1:- (i) Find the power dissipation in a resistor also give its units.

(ii) How many electron pass through an electric bulb in one minute if the 300mA current is passing through it?

Q.No.2: -(i) State and explain electromotive force and internal resistance of a source of emf. Also calculate the emf for a source of emf. Why potential difference is less than the emf. 

(ii) A charge of 90 C passes through a wire in 1 hour and 15 minutes. What is the current in the wire?

Short Questions for fsc 2nd year 13 chapter current electricity

Q.No.2: -Write the brief answers of the following questions.  Attempt Any 4  (mark 8)

(i) Why does the resistance of a conductor rise with temperature?

(ii) Do bends in a wire affects its electrical resistance?

(iii) Is the filament resistance lower or higher in a 500W, 220V light bulb in a 100W bulb?
(iv) How the heat produced when current flows in a conductor, on which factors the heat of the resistance depends?

(v) Define ohm law. Why the ohmic device doesn’t exist?

(vi) Draw the graph between current and voltage for semiconductor diode and also describe that why the graph turn towards current axis and not toward the voltage axis?

(vii) Define current also write its unit.

M.C.Q's Chapter No 13 Current Electricity 2nd year

Q.No.1: - Tick the correct answer.                        Mark 10

(i) Which type of energy is stored in a cell?

(a) Heat energy       (b) Potential energy     (c) Kinetic Energy        (d) Chemical energy

(ii) The pattern of magnetic field formed around a straight conductor is

(a) Circular              (b) elliptical                 (c) bar magnetic            (d) non of these

(iii) We can find resistance from the Ohm law by using the relation

(a) R=VI                  (b) R=V/I                     (c) V=IR                       (d) No of these

(iv) When the resistors are connected in series then the equivalent resistance will be equal to the

(a) sum of resistances   (b) sum of the reciprocal of all the resistances (c) average of the resistances (d) zero

(v) the units of conductivity is

(a) (ohm.m)^-1           (b) mho.m^-1                 (c) m.ohm^-1                    (d) both (a) and (b)

(vi) The resistivity is directly proportional to the

(a) Square of the area of the conductor (b) inverse of the resistance of the conductor

(c) Inverse of length of conductor (d) current of the conductor

(vii) On the resistor the silver band shows the tolerance of

(a) 5%                    (b) 7%                          (c) 10%                          (d) 20%

(viii) The power dissipation in a resistor is equal to

(a) P=VI                (b) P=V²I                     (c) P=R²I                       (d) P=V²/I

(ix) The resistance of a resistor with color code first “red” second “violet” third “orange” forth “silver”

(a) 47000 Ω           (b) 4000 Ω                    (c) 2700 Ω                     (d) 3700 Ω

(x) The color code of “Yellow” on a resistor is

(a) 1                       (b)4                               (c)8                                  (d) 3 

Q.No.3.9: - Define impulse and show that how it is related to linear momentum?

Q.No.3.9: - Define impulse and show that how it is related to linear momentum?

Ans: - Impulse: -  If a very large force exert for a very short interval of time then product of such force and time is called impulse.

     Mathematically

Relation between impulse and linear momentum: -  

            According to Newton’s second law of motion, the force is defined as the rate of change of momentum.

          Thus if force F acting on a body for time ∆t, changes its momentum from mv_f to mv_i. Then the force is written as;



Hence, impulse is equal to the change of linear momentum.

Q.No.3.8: - Find the change in momentum for an object subjected, to a given force for a given time and state lawof motion in terms of momentum.

Q.No.3.8: - Find the change in momentum for an object subjected, to a given force for a given time and state lawof motion in terms of momentum.

Ans: - Consider a body of mass “m” moving with an initial velocity v_i. Let us suppose that an external force F acts upon it for time “t” after which velocity becomes v_f. If this force produces an acceleration a, then it is expressed as,



This is Newton’s 2^nd law in terms of momentum.

Q.No.3.13: - At what point or points in its path does a projectile have its minimum speed, its maximum speed?

Q.No.3.13: - At what point or points in its path does a projectile have its minimum speed, its maximum speed?

Ans: - (i) The speed of projectile is minimum at the maximum height because the vertical component is zero at the maximum height.

 (ii) The speed of a projectile is maximum at the point of projection and also just before it strikes the ground (level of projection) because the vertical component of velocity v_y is maximum at these points.

Q.No.3.12:- Explain what is meant by projectile motion. Derive expressions for (a) the time of flight (b) the range of projectile. Show that the range of projectile is maximum when projectile is thrown at an angle of 450 with the horizontal.

Q.No.3.12:- Explain what is meant by projectile motion. Derive expressions for (a) the time of flight (b) the range of projectile. Show that the range of projectile is maximum when projectile is thrown at an angle of 45⁰ with the horizontal.

Ans: - in the book

Q.No.3.11: - Explain the difference between elastic and inelastic collisions. Explain how would a bouncing ball behave in each case? Give plausible reasons for the fact that K.E is not conserved in most cases?

Q.No.3.11: - Explain the difference between elastic and inelastic collisions. Explain how would a bouncing ball behave in each case? Give plausible reasons for the fact that K.E is not conserved in most cases?

Ans: - Elastic Collision:-

                                Such a collision in which K.E and linear momentum remain same before and after collision is called elastic collision.

Inelastic Collision: -

                        Such a collision in which K.E and linear momentum does not remain same before and after collision is called inelastic collision.

         If the bounding ball collide with the floor in such a way that it rebounds to the initial height then its collision will be elastic because both K.E and linear momentum will remain same but if it does not rebound to the same height then this collision will be inelastic collision because much of the momentum will be change before and after collision.

               In most of the cases the K.E is not conserved because if we think for a moment then we arrive at a result that elastic collision is an ideal one. K.E does not conserved because of some frictional effects and much of the K.E is lost in the form of sound, heat and work done against the colliding object etc…

NoQ..3.10: - State the law of conservation of linear momentum, pointing out the importance of isolated system. Explain, why under certain conditions, the law is useful even though the system is not completely isolated?

NoQ..3.10: - State the law of conservation of linear momentum, pointing out the importance of isolated system. Explain, why under certain conditions, the law is useful even though the system is not completely isolated?

Ans: - Statement:-

                       It states that the total linear momentum of an isolated system always remains constant.

            Isolated system is important in many respects we study the properties of gases in an isolated system. Firing a bullet from a gun, the shooting of missile etc… The isolated system is an ideal system and such ideal systems do not exist. The momentum tells us about the motion of the bodies. So if we want to know the motion of bodies then we use this law and ignore the external force on the system.

Q.No.3.7: - Motion with constant velocity is a special case of motion with constant acceleration. Is this statement true? Discuss.

Q.No.3.7: - Motion with constant velocity is a special case of motion with constant acceleration. Is this statement true? Discuss.

Ans: -  Yes this statement is true because when the body moves with constant velocity then its acceleration will be zero and zero is itself a constant value so we can say that acceleration is also constant during constant velocity.

Q.No.3.6: - Explain the circumstances in which the velocity v and acceleration a of a car are (i) Parallel (ii) Anti-parallel (iii) Perpendicular (iv) v is zero but a is not zero. (v) a is zero but v is not zero.

Q.No.3.6: - Explain the circumstances in which the velocity v and acceleration a of a car are

(i) Parallel    (ii) Anti-parallel      (iii) Perpendicular     (iv) v is zero but a is not zero.    (v) a is zero but v is not zero.

Ans: - (i) When the car is moving with increasing velocity then the direction of acceleration will be parallel to the velocity.

(ii) When the car is moving with decreasing velocity then the direction of acceleration will be anti-parallel to the velocity. ( the direction of velocity depends upon the change in displacement so when the body move slowly then it will move in the forward direction but change in displacement will be in the forward direction. On the other hand the direction of acceleration depends upon the direction of change in velocity and in this case the velocity of the car is decreasing so the direction of acceleration will be opposite to the direction of velocity)

(iii) When the car will move in a circle then the direction of velocity and acceleration will be perpendicular to each other. ( in this case the direction of velocity will be along the tangent to the circle and the direction of acceleration depends upon the change in velocity so if we take the vector sum then the resultant will always point toward the center of the circle so we can say that velocity and acceleration will be perpendicular to each other in this case )

(iv) When the brakes are applied on the moving car, it slows down and comes to rest due to negative acceleration in the opposite direction. Thus, velocity v is zero but a is not zero.

(v) When the car is moving with constant velocity then there will be no change in velocity so acceleration will be zero but velocity will not be zero.

Q.No.3.5: - A man standing on the top of a tower throws a ball straight up with initial velocity Vi and at the same time throws a second ball straight downward with the same speed. Which ball will have larger speed when it strikes the ground ignore air friction?

Q.No.3.5: - A man standing on the top of a tower throws a ball straight up with initial velocity V_i and at the same time throws a second ball straight downward with the same speed. Which ball will have larger speed when it strikes the ground ignore air friction?

Ans: - Both balls will have same speed on striking the ground. When a body is projected vertically upward with certain initial velocity, then it will hit the ground with the same velocity. Thus, when the ball is thrown straight up with the initial velocity v_i when it returns back. Hence, this ball will strike the ground with the same speed. When a second ball is thrown vertically downward with initial velocity v_i it will also strike the ground with the same speed. It results that, in both the cases, the balls will hit the ground with the same speed. But the difference is that both the balls will hit the ground at different times due to different heights.

Q.No.3.4: - Specify the correct statement:- (a) An object can have a constant velocity even its speed is (a) An object can have a constant velocity even its speed is (a) An object can have a constant velocity even its speed is Changing (b) An object can have a constant speed even its velocity is Changing. (c) An object can have a zero velocity even its acceleration is not zero.(d) An object subjected to a constant acceleration can reverse its velocity.

Q.No.3.4: - Specify the correct statement:-

                 (a)      An object can have a constant velocity even its speed is  Changing.

(b)           An object can have a constant speed even its velocity is

Changing

(c)            An object can have a zero velocity even its acceleration is not zero.

(d)           An object subjected to a constant acceleration can reverse its velocity.

Ans: - The correct answer is (b).

Q.No.3.3: - Can the velocity of an object reverse direction when acceleration is constant? If so, give an example.

Q.No.3.3: - Can the velocity of an object reverse direction when acceleration is constant? If so, give an example.

Ans: - Yes, it is possible that the velocity of an object reverse direction when acceleration is constant. For example when we throw a body upward then the direction of acceleration will be downward while acceleration remains same.

Q.No.3.2: - An object is thrown vertically upward. Discuss the sign of acceleration due to gravity relative to velocity, while the object is in air.

Q.No.3.2: - An object is thrown vertically upward. Discuss the sign of acceleration due to gravity relative to velocity, while the object is in air.

Ans: - When the object is thrown vertically upward then the body will displace in the upward direction so the direction of velocity is in the upward direction but we noticed that after covering so vertical upward distance the body will slow which shows that the velocity decrease. At this time the direction of acceleration will be downward because the direction of change in velocity is downward.

          During the downward flight  we noticed that the body we move rapidly from the extreme position which means that the velocity will increase and at that time the direction of acceleration will be toward the downward direction. So we can say that in both the flights the sign of gravitational acceleration “g” is downward.

Q.No.3.1: - What is the difference between uniform and variable velocity. From the explanation of variable velocity, define acceleration. Give SI units of velocity and acceleration.

Q.No.3.1: - What is the difference between uniform and variable velocity. From the explanation of variable velocity, define acceleration. Give SI units of velocity and acceleration.

Ans: -

Uniform Velocity: -

                      If a body covers equal displacements in equal intervals of time, however small may be, the body is said to have uniform velocity. Its motion is said to be uniform. But be remember that the direction of body all also remain same. If one of them (magnitude or direction) changes then the body will not move with uniform velocity.

Variable Velocity: -

                       If a body covers unequal displacements in equal intervals of time it is said to be moving with variable velocity. If the body is moving in such a way that the magnitude of its velocity is same but its direction is changing then the body is said to be moving with variable velocity.

Acceleration: -  

                   Time rate of change of velocity of a body is called acceleration. This means that the velocity is changing, so from the definition of variable velocity we can say that variable velocity is also called acceleration.

SI Units: - The SI units of velocity are m/s.

                   The SI units of acceleration are ms^-2.