Pre-Test Exam-2022_Physics_CQ_EV_Sample Questions
Page 1 of 2
Subject Code: 1 7 4
B A F Shaeen College Dhaka Pretest Examination-2022
Sample Question
Subject: Physics (Creative Question)
Time: Full Marks:50 [Five questions have to be answered(at least two questions from each sections)]
Section-A
1. To reach the other side of the river two boat men start with the velocity 5kmh-1 and 4kmh-1
respectively making angle 300 and 500 with the water current. The water current velocity is 3kmh-1 and the width of the river is 5km.
a) What is called divergence?
b) In case of electric fan the air flows down. Why?
c) Find the distance between destinations of two boatmen.
d) If there is no water current, going after 15 minutes if they start going to each other, then is it possible to meet themselves within 5 minutes?
2.
In a car forces are applied according to figure. After 2minutes the action of force is stopped and then the car moves with velocity √3 ms-1 in the same direction. An observer in the car saw a bus is moving towards the west with a velocity 1ms-1. The mass of the car 1500kg.
a) Define unlike vector.
b) Explain the physical properties of divergence.
c) In 2 minutes find the acceleration of the car.
d) Is there any possibility of collision between bus and a truck which is moving with velocity 2ms-1 making angle 300 with the north towards the west?
3. A dancer revolving herself with respect to her own axis with a velocity 1revs-1 by expanding her hands. If she compressed her hands the moment of inertia decreased by 60%. If she does not change the position of her hands, she would not be able to change her angular velocity but due to apply an external torque the velocity must be changed.
a) Define work-energy theorem.
b) The efficiency of an engine can never be 100%. Explain.
c) Find the number of revolutions per second in hand compressed condition.
d) Analysis the last statement given in the stem.
4.
North South
East West
300
600 500N
250N
500N 1000N
P
Pre-Test Exam-2022_Physics_CQ_EV_Sample Questions
Page 2 of 2
According to figure an object of mass 8 × 10−3𝑘g is tied at the end of the spring and is stretched by 6
× 10−2m from equilibrium to point P. k=320Nm-1 a) Define conservative force.
b) If the magnitude and direction both are variable, then how is the work done measured?
c) In stretched position find the potential energy of the spring.
d) When the spring returns to equilibrium from the compressed state, compare the velocity of object at point ‘A’ and equilibrium position.
Section: B
5. A piece of ice of mass mkg is fallen from a height of 20km. 50% of its total energy is converted into heat and some part of the ice melts. Latent heat of melting of ice is 80000calkg−1 and mechanical equivalent of heat is
4 . 2 Jcal
−1.a) Define internal energy.
b) Explain the efficiency of the refrigerator.
c) What percentage of ice melts?
d) If the ice is fallen from a certain height, then it melts fully. Analysis mathematically.
6. The radius of the sphere is 15cm.
a) State the gauss’ law.
b) If a positive charge is displaced along the perpendicular bisector of an electric pole, there will not be work done. Explain the reason.
c) Find the electric intensity at point ‘P’ due to charge q1.
d) If a wire of resistance 15 is connected between C and D, then 5A current will flow. Justify.
7. In Young’s double slit experiment the distance of 4th bright fringe is 0.2510−3m. The slit separation is 1mm and screen distance is 1m.
a) Define Poynting vector.
c) What happened if a white light is incidence in spite of monochromatic light in case of diffraction of grating?
d) Whether the fringe is bright or dark at distance 6.0312510−3m from the central fringe? Analysis mathematically.
8. Rony and Jony perform an experiment of diffraction grating individually. The no lines in Rony’s grating is 6000cm−1 and in Jony’s grating is 1.25105cm−1. Rony use the light of wavelength
5896A0 and Jony use 2000A0. Then Jony bring some change in his experiment so that in their experiment 2nd order maxima are formed at an same diffraction angle.
a) What is electromagnetic spectrum?
b) If phase difference of two waves is not same always, the interference is seen properly. Explain.
c) Find the diffraction angle of first order maximu in Rony’s experiment.
d) Analysis the change which is brought in Jony’s experiment.
