Motion Worksheet-17

Motion Worksheet-17

41. (a) Define velocity. What is the SI unit of velocity?

(b) What is the difference between speed and velocity?

(c) Convert a speed of 54 km/h into m/s.

42. (a) What is meant by the term ‘acceleration’? State the SI unit of acceleration.

(b) Define the term ‘uniform acceleration’. Give one example of a uniformly accelerated motion.

43. The distance between Delhi and Agra is 200 km. A train travels the first 100 km at a speed of 50 km/h. How fast must the train travel the next 100 km, so as to average 70 km/h for the whole journey?

44. A train travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h. Calculate the average speed for the entire train journey.

45. A car is moving along a straight road at a steady speed. It travels 150 m in 5 seconds:

(a) What is its average speed?

(b) How far does it travel in 1 second?

(c) How far does it travel in 6 seconds?

(d) How long does it take to travel 240 m?

46. A body is moving along a circular path of radius R. What will be the distance travelled and displacement of the body when it completes half a revolution?

47. If on a round trip you travel 6 km and then arrive back home :

(a) What distance have you travelled?

(b) What is your final displacement?

48. A body travels a distance of 3 km towards East, then 4 km towards North and finally 9 km towards East.

(i) What is the total distance travelled?

(ii) What is the resultant displacement?

49. A boy walks from his classroom to the bookshop along a straight corridor towards North. He covers a distance of 20 m in 25 seconds to reach the bookshop. After buying a book, he travels the same distance in the same time to reach back in the classroom. Find (a) average speed, and (b) average velocity, of the boy.

50. A car travels 100 km at a speed of 60 km/h and returns with a speed of 40 km/h. Calculate the average speed for the whole journey.

51. A ball hits a wall horizontally at 6.0 m/s^–1. It rebounds horizontally at 4.4 m/s^–1. The ball is in contact with the wall for 0.040 s. What is the acceleration of the ball?

52. (a) What remains constant in uniform circular motion?

(b) What changes continuously in uniform circular motion?

53. State whether the following statement is true of false :

Earth moves round the sun with uniform velocity.

54. A body goes round the sun with constant speed in a circular orbit. Is the motion uniform or accelerated?

55. What conclusion can you draw about the acceleration of a body from the speed-time graph shown below :

56. Name the quantity which is measured by the area occupied under the velocity-time graph.

57. What does the slope of a speed-time graph indicate?

58. What does the slope of a distance-time graph indicate?

59. Give one example of a motion where an object does not change its speed but its direction of motion changes continuously.

60. Name the type of motion in which a body has a constant speed but not constant velocity.

Answer:

41. Rate of change of position i.e. rate of displacement with time is called velocity.

Speed is a scalar quantity and velocity is a vector quantity.

(c) 15 m/s

42. –

43. 116.6 km/h

44. 40 km/h

45. (a) 30 m/s  (b) 30 m   (c) 180 m   (d) 8 s

46. πR; 2R

1. Suppose the particle traveled only from A to B. Then distance = πr, but displacement = 2r.

47. (a) 6 km   (b) zero

48. (i) 16 km   (ii) 12.6 km

49. Average speed = 0.8 m/s; Average velocity = 0 m/s as displacement is zero.

50. 48 km/h

2 × 60 × 40/(60 + 40)

51. -260 ms^–2

52. (a) Speed (b) Direction of motion

53. false

54. Accelerated

55. Non-uniform acceleration

56. Distance travelled by the moving body

57. Acceleration

58. Speed

59. Movement around a circular track.

60. Uniform circular motion