What conclusion can you draw about the velocity of a body from the displacement-time graph shown below : - It represents uniform velocity., A satellite goes around the earth in a circular orbit with constant speed. Is the motion uniform or accelerated? - It is accelerated motion as the velocity is changing continuously., i. A snail covers a distance of 100 metres in 50 hours. Calculate the average speed of a snail in km/h. ii. A tortoise moves a distance of 100 metres in 15 minutes. What is the average speed of tortoise in km/h? iii. If a sprinter runs a distance of 100 metres in 9.83 seconds, calculate his average speed in km/h. - Average speed = Total distance travelled/ Total time taken Total distance travelled = 100m = 0.1 km; Total time taken = 50 hr Average speed= 0.1/50=0.002km/h. Same way you can find the average speed of tortoise and sprinter, Bus X travels a distance of 360 km in 5 hours whereas bus Y travels a distance of 476 km in 7 hours. Which bus travels faster? - For bus X, Speed=360/5=72km/h, For bus Y, Speed=476/7=68 km/h  Speed of bus X is more than that of bus Y. Hence, bus X travels faster., A train starting from rest moves with a uniform acceleration of 0.2 m/s2 for 5 minutes. Calculate the speed acquired and the distance travelled at this time. - Initial velocity, u=0m/s, a=0.2 m/s2, t=5min= 5 x60=300 sec, Using, v = u + at v =0 + 0.2 x 300=60m/s, And the distance travelled is s= ut+1/2at2 = 9 km, Draw a velocity-time graph to show the following motion: A car accelerates uniformly from rest for 5 s; then it travels at a steady’ velocity for 5 s., The velocity-time graph for part of a train journey is a horizontal straight line. What does this tell you about (a) the train’s velocity, and (b) its acceleration? - (a) The train has a uniform velocity. (b) There is no acceleration., The graph given alongside shows the positions of a body at different times. Calculate the speed of the body as it moves from : (i) A to B, (ii) B to C, and  (iii) C to D.   - i) The distance covered from A to B is( 3-0) =3 cm, Time = 3s, Speed = distance / time= 1cm/s (ii) The speed of the body as it moves from B to C is zero. (iii) The distance covered from C to D is (7-3) = 4 cm, Time =2s, Speed = distance/time= 4cm/2s= 2cm/s  , Given alongside is the velocity-time graph for a moving body: Find (i) Velocity of the body at point C. (ii) Acceleration acting on the body between A and B (iii) Acceleration acting on the body between B and C.   - (i) BC represents uniform velocity. From graph, we see that the velocity of the body at point C = 40km/h  (ii) Acceleration between A and B = slope of line AB (iii) BC represents uniform velocity, so acceleration acting on the body between B and C is zero.  , A body is moving uniformly in a straight line with a velocity of 5 m/s. Find graphically the distance covered by it in 5 seconds. - Distance travelled = Area of rectangle OABC = OA x OC  =5 x 5 =25 m,

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