CBSE Class 9 Science Past Paper PDF 2019-2020

Chap 8 : Motion www.cbse.online CHAPTER 8 File Revision Date : 10...

Chap 8 : Motion www.cbse.online CHAPTER 8 File Revision Date : 10 July 2019 CBSE Objective Questions Exam 2019-2020 CLASS : 9th SUB : Science For more subject visit www.cbse.online or whatsapp at 8905629969 Motion 1. OBJECTIVE QUESTIONS straight line at time t is given by x = a0 + a1 t + a2 t2 What is the acceleration of the particle ? 1. A graph is plotted showing of a car as a function of (a) a1 (b) a2 time. If the graph is a straight line, it means that (c) 2a2 (d) 3a2 (a) the car started at rest (b) acceleration was constant Ans : (c) 2a2 (c) acceleration was increasing v = dx = a1 + 2a2 t dt (d) velocity was constant ` a = dv = 2a2 Ans : (b) acceleration was constant dt 2. If the initial velocity of an object is equal to final 6. In a long distance race, the athletes were expected velocity, the value of acceleration is to take four rounds of the track such that the line of (a) positive (b) negative finish was same as the line of start. Suppose the length (c) zero (d) infinite of the track was 200 m. The what is the displacement of the athletes when they touch the finish line? Ans : (c) zero (a) zero (b) 3 m NO NEED TO PURCHASE ANY BOOKS (c) 5 m (d) 7 m For session 2019-2020 free pdf will be available at Ans : (a) zero www.cbse.online for Displacement = 0 (zero), as athletes finish at the 1. Previous 15 Years Exams Chapter-wise Question starting line. Bank 2. Previous Ten Years Exam Paper (Paper-wise). 7. When an object travels equal distances in equal 3. 20 Model Paper (All Solved). intervals of time, howsoever small the interval may 4. NCERT Solutions be, the motion of the object is said to be All material will be solved and free pdf. It will be (a) uniform (b) non-uniform provided by 30 September and will be updated regularly. (c) circular motion (d) oscillatory motion Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education, New Delhi in any manner. www.cbse.online is a private organization which provide free study material pdfs to students. At www.cbse.online CBSE stands for Canny Books Ans : (a) uniform For School Education 8. Which of the following is an example of non-uniform acceleration? 3. A body thrown vertically upwards reaches a maximum (a) The motion of a bicycle going down the slope of height h. It then returns to ground. The distance and a road when the rider is not pedalling and wind the displacement travelled by the body respectively resistance is negligible. are (b) The motion of a ball rolling down an inclined (a) 2h , zero (b) h , zero plane. (c) zero, 2h (d) zero, h (c) The motion of a freely falling body. Ans : (a) 2h , zero (d) The movement of a car in a crowded road. Distance = h + h = 2h Ans : (d) The movement of a car in a crowded road. Displacement = h - h = zero 9. A quantity has a value of - 6.0 m/s. It may be the 4. If a car is traveling north on a straight road and its (a) speed of a particle brakes are applied, it will (b) velocity of a particle (a) have no acceleration (c) position of a particle (b) accelerate to the south (d) displacement of a particle (c) accelerate to the north Ans : (b) velocity of a particle (d) accelerate either east or west If a body travels equal distances in equal intervals of Ans : (b) accelerate to the south time, how so ever small these intervals may be, then the body is said to be moving with uniform speed. 5. The displacement x of a particle moving along a This motion is known as uniform motion. Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 52 Chap 8 : Motion www.rava.org.in 10. Which of the following options is correct for the time graph is a object having a straight line motion represented by (a) straight line (b) circle the following graph? (c) stair-like (d) polygon Ans : (a) straight line 13. The distance-time graph of an object moving in a fixed direction is shown in graph. The object (a) The object moves with constantly increasing velocity from O to A and then it moves with constant velocity. (b) Velocity of the object increases uniformly. (a) is at rest (c) Average velocity is zero. (b) moves with a constant velocity (d) The graph shown is impossible. (c) moves with a variable velocity Ans : (c) Average velocity is zero. (d) moves with a constant acceleration From given, it is clear that the net displacement is zero. So, average velocity will also be zero. Ans : (b) moves with a constant velocity For more files visit www.cbse.online For more files visit www.cbse.online 11. An object is sliding down an inclined plane. The 14. The distance-time graph of an object is shown in velocity changes at a constant rate from 10 cm/s to 15 graph. The object cm/s in two seconds. What is its acceleration? (a) 10 cm/s2 (b) 2.9 cm/s2 (c) 2.5 cm/s2 (d) 40 cm/s2 (a) is at rest Ans : (c) 2.5 cm/s2 (b) moves with a constant speed The situation is shown in figure. Let us take BA (c) moves with a variable velocity as the positive direction. The velocity at t = 0 is u = + 10 cm/s and that at t = 2 s is v =+ 15 cm/s. (d) moves with a constant acceleration Thus, Ans : (a) is at rest 15. If a body is moving at constant speed in a circular path, its (a) velocity is constant and its acceleration is zero (b) velocity and acceleration are both changing direction only (c) velocity and acceleration are both increasing (d) velocity is constant and acceleration is changing direction The acceleration is positive, which means it is in the direction BA. Ans : (b) velocity and acceleration are both changing direction only For more files visit www.cbse.online 16. The area under speed-6time graph represents a 12. If a particle moves with a constant speed, the distance- physical quantity whose unit is equal to the unit of (a) light year (b) area Get all GUIDE and Sample Paper PDFs by whatsapp from +918905629969 Page 53 Chap 8 : Motion www.cbse.online (c) volume (d) acceleration 19. If a body moves with uniform velocity, then the acceleration is equal to Ans : (a) light year (a) zero (b) constant The area under speed-time graph represents distance and the unit of distance is metre (m), which is same as (c) finite (d) infinite the unit of light year (1ly = 3.15 # 107 m). Ans : (a) zero We know that 17. The graph shows the variation of velocity of a rocket with time. Then, the maximum height attained by the Change in velocity Acceleration = Time rocket is When a body moves with a uniform velocity then the value of change in the velocity is zero. Hence acceleration is also zero. 20. The displacement of a particle is given by y = a + bt + ct2 - dt 4 The initial velocity and acceleration are respectively (a) b, - 4d (b) - b, 2c (c) b, 2c (d) 2c, - 4d Ans : (c) b, 2c dy v = = b + 2ct - 4dt3 dt (a) 1.1 km (b) 5 km v0 = b + 2c ^0 h - 4d ^0 h3 = b (c) 55 km (d) none of these (a for initial velocity, t = 0 ) Ans : (c) 55 km Now a = dv = 2c - 12dt2 dt Maximum height = 1 # 110 # 1000 = 55 km a0 = 2x - 12d ^0 h2 = 2c , (at t = 0 ) 2 ` NO NEED TO PURCHASE ANY BOOKS 21. Which of the following speed time graphs is not For session 2019-2020 free pdf will be available at possible ? www.cbse.online for 1. Previous 15 Years Exams Chapter-wise Question Bank 2. Previous Ten Years Exam Paper (Paper-wise). 3. 20 Model Paper (All Solved). 4. NCERT Solutions All material will be solved and free pdf. It will be provided by 30 September and will be updated regularly. Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education, New Delhi in any manner. www.cbse.online is a private organization which provide free study material pdfs to students. At www.cbse.online CBSE stands for Canny Books For School Education 18. If a car at rest accelerates uniformly to a speed of 144 km/h in 20 sec., it covers a distance of (a) 20 cm (b) 400 m (c) 1440 cm (d) 2980 cm Ans : (c) Ans : (b) 400 m This is because speed can never be negative. v = =144 # 1000 G m/ sec. ^60 # 60h 22. If the motion is in straight line without change in direction then v = u + at (a) distance ! displacement ^144 # 1000h (b) distance 2 displacement or = 0 + a # 20 ^60 # 60h (c) distance 1 displacement ` a = 144 # 1000 (d) distance = displacement 60 # 60 # 20 Ans : (d) distance = displacement = 2 m/ sec2 In the straight line motion distance is always equal to Now s = ut + 1 at2 the displacement. 2 23. A passenger travels along the straight road for half = 0 + 1 # 2 # ^20h2 = 400 m 2 the distance with velocity v1 and the remaining half Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 54 Chap 8 : Motion www.rava.org.in distance with velocity v2. Then average velocity is.......... given by Ans : 4 : 9 2 (a) v1 v2 (b) v22 v1 7. If a car starts at rest and accelerates uniformly, the ^v1 + v2h (c) (d) 2v1 v2 distance it travels is proportional to the.......... of the 2 ^v1 + v2h time it travels. 2v1 v2 Ans : square Ans : (d) ^v1 + v2h For more files visit www.cbse.online x +x 2 2 = 1 = 2v1 v2 8. The speed-time graph of a moving object is a straight x + x v2 + v1 v1 + v2 2v1 2v2 d n line parallel to the time-axis. It means the speed is 2v1 v2.......... 24. A particle covers half of the circle of radius r. Then Ans : uniform the displacement and distance of the particle are respectively 9. If a car is going northward and the driver jams on its (a) 2pr, 0 (b) 2r, pr brakes, the direction of its acceleration is.......... (c) p r , 2r (d) pr, r Ans : south 2 Ans : (b) 2r, pr 10. A body moving with a uniform speed along a circle has.......... velocity. Ans : variable 3. TRUE/FALSE 1. A particle is known to be at rest at time t = 0. If its acceleration at t = 0 must be zero. Ans : False When a particle cover half of circle of radius r , then 2. Magnitude of acceleration is constant in the rotating displacement is AB = 2r motion along a circular path. distance = half of circumference of circle = pr Ans : True 2. FILL IN THE BLANK 3. The equation s = ut + 12 at2 with the usual notation is vectorial in nature. Ans : True 1. The magnitude of average velocity.......... equal to the average speed. 4. Magnitude of displacement can be equal to or lesser Ans : may or may not be than distance. Ans : True 2. Distance travelled divided by elapsed time gives.......... 5. In a journey, numerical value of displacement # Ans : average speed distance. Ans : True 3. A body, dropped from a tower with zero velocity, reaches the ground in 4 sec. The height of the tower 6. If particle speed is constant, acceleration of the is about.......... m particle must be zero. Ans : 80 Ans : False 4. A ball thrown vertically upwards return to its starting 7. A particle moving with a uniform velocity must be point in 4s. If g = 10 m/s2 , its initial speed was.......... along a straight line. Ans : 20 m/s Ans : True 5. When negative acceleration acts on a moving body its 8. A particle in one dimensional motion with positive velocity.......... value of acceleration must be speeding up. Ans : decreases Ans : False 6. A stone is let to fall from a building of height 30m. 9. Area under velocity-time graph shows displacement. The ratio of heights fallen by it after 2s and 3s is Ans : True Get all GUIDE and Sample Paper PDFs by whatsapp from +918905629969 Page 55 Chap 8 : Motion www.cbse.online 4. MATCHING QUESTIONS 5. ASSERTION AND REASON DIRECTION : In the section, each question has two matching DIRECTION : In each of the following questions, a statement lists. Choices for the correct combination of elements from of Assertion is given and a corresponding statement of Reason List-I and List-II are given as options (a), (b), (c) and (d) out of is given just below it. Of the statements, given below, mark the which one is correct. correct answer as: (a) Both assertion and reason are true and reason is 1. Match the Column the correct explanation of assertion. Column-I Column-II (b) Both assertion and reason are true but reason is not the correct explanation of assertion. (A) Uniform speed (p) Unequal distance (c) Assertion is true but reason is false. in equal time (d) Both Assertion and Reason are false. (B) Constant speed (q) Zero acceleration 1. Assertion : An object may acquire acceleration even if (C) Uniform (r) Unequal velocity in it is moving at a constant speed. acceleration equal time change Reason : With change in the direction of motion, an (D) Non-uniform (s) Equal distance in object can acquire acceleration. acceleration equal time Ans : (a) Both assertion and reason are true and (E) Non-uniform speed (t) Equal velocity reason is the correct explanation of assertion. change in equal This is the equation of a parabola. A parabola results time when one quantity is proportional to the square of the other. When an object is moving with a constant Ans : (A) - (s), (B) - (q), (C) - (t), (D) - (r), (E) velocity (zero acceleration), the displacement versus - (p) time graph is a straight line and its slope is velocity. When an object is moving at a constant speed but 2. its direction of motion changes, its velocity changes ant thus acceleration is produced. Motion of an object Column-I Column-II in a circular path is such an example. In a uniform (A) Average velocity (p) v-u circular motion, the direction of motion of the object T changes continuously and hence the velocity changes (B) Acceleration (q) D continuously even though the speed is constant. T 2. Assertion : Displacement of an object may be zero (C) Final velocity (r) ut + 1 at2 even if the distance covered by it is not zero. 2 Reason : Displacement is the shortest distance between (D) Distance (s) v+u the initial and final position. t Ans : (a) Both assertion and reason are true and (E) Speed (t) u + at reason is the correct explanation of assertion. When the final position of an object coincides with its Ans : (A) - (s), (B) - (p), (C) - (t), (D) - (r), (E) initial position, displacement is zero, but the distance - (q) travelled is not zero. 3. 3. Assertion : The graph between two physical quantities P and Q is straight line, when P/Q is constant. Column-I Column-II Reason : The straight line graph means that P is proportional to Q or P is equal to constant multiplied (A) Slope of (p) Acceleration by Q. displacement-time graph Ans : (a) Both assertion and reason are true and reason is the correct explanation of assertion. (B) Slope of velocity- (q) Velocity According to statement of reason, as the graph is a time straight line, P ? Q , or, P = constant # Q (C) Area under (r) Change in velocity P/Q = constant velocity-time Equation of a straight line is y = mx + c graph intercepted with time-axis 4. Assertion : Velocity versus time graph of a particle in uniform motion along a straight path is a line parallel (D) Area under (s) Displacement to the time axis. acceleration-time Reason : In uniform motion the velocity of a particle graph intercepted increases as the square of the time elapsed. with time-axis Ans : (c) Assertion is true but reason is false. (t) Speed When a particle is in uniform motion, the magnitude of its velocity at each instant such as t = 0 , t = 1s , Ans : (A) - (q), (B) - (p), (C) - (s), (D) - (r) Download all GUIDE and Sample Paper pdfs from www.cbse.online or www.rava.org.in Page 56 Chap 8 : Motion www.rava.org.in t = 2s..... etc. is always constant. Hence the velocity is not the correct explanation of assertion. versus time graph for a particle in uniform motion Displacement may be positive, negative or zero. along a linear path is a straight line parallel to the Displacement is a vector quantity. time axis. 10. Assertion : When the displacement of a body is 5. Assertion : the speedometer of a car measures the directly proportional to the square of the time. Then instantaneous speed of the car. the body is moving with uniform acceleration. Reason : Average speed is equal to the total distance Reason : The slope of velocity-time graph with time covered by an object divided by the total time taken. axis gives acceleration. Ans : (b) Both assertion and reason are true but reason Ans : (b) Both assertion and reason are true but reason is not the correct explanation of assertion. is not the correct explanation of assertion. The speedometer of a car measures the instantaneous For more files visit www.cbse.online speed of the car. NO NEED TO PURCHASE ANY BOOKS 6. Assertion : An object may have acceleration even if it is moving with uniform velocity. For session 2019-2020 free pdf will be available at Reason : An object may be moving with uniform www.cbse.online for velocity but it may be changing its direction of motion. 1. Previous 15 Years Exams Chapter-wise Question Bank Ans : (a) Both assertion and reason are true and 2. Previous Ten Years Exam Paper (Paper-wise). reason is the correct explanation of assertion. 3. 20 Model Paper (All Solved). The uniform motion only means that the object is 4. NCERT Solutions moving at a constant speed but its direction of motion All material will be solved and free pdf. It will be may be changing at in the case of uniform circular provided by 30 September and will be updated regularly. motion. Hence, acceleration is produced in uniform Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education, New Delhi in any manner. www.cbse.online is a private organization which provide free motion due to changes in velocity. study material pdfs to students. At www.cbse.online CBSE stands for Canny Books For School Education 7. Assertion : Motion with uniform velocity is always along a straight line path. Reason : In uniform velocity a motion, speed is the magnitude of the velocity and is equal to the instantaneous velocity. Ans : (b) Both assertion and reason are true but reason is not the correct explanation of assertion. The assertion is true and the reason is not the correct explanation of the assertion. Uniform velocity means that speed and direction remain unchanged. 8. Assertion : If a particle is moving with constant velocity, then average velocity for any time interval is equal to instantaneous velocity. Reason : If average velocity of a particle moving on a straight line is zero for a given time interval, then instantaneous velocity at some instant within this interval may be zero. Ans : (b) Both assertion and reason are true but reason is not the correct explanation of assertion. Average velocity Vav Total displacement Vt = = =V Total elapsed time t = Instantaneous velocity Hence, assertion is correct. If a particle is in a round trip on a straight line, then average velocity is zero but at the instant at which the particle reverses its direction of motion, velocity is zero. So, reason is correct. But reason is not the correct explanation of assertion. 9. Assertion : The displacement of an object can be either positive, negative or zero. Reason : Displacement has both the magnitude and direction. Ans : (b) Both assertion and reason are true but reason Get all GUIDE and Sample Paper PDFs by whatsapp from +918905629969 Page 57