The distance between the Earth and the Sun is 14 , 90 , 00 , 000 km . The speed of light is 3 × 10 8 m / s . The sun stops giving out light now, how much longer will we be able to see the Sun?

Given that, Speed of the light = 3 × 10 8 m s - 1 = 3 × 10 5 km s - 1 Distance between earth and sun = 14 , 90 , 00 , 000 km We know that, Speed = Distance covered Time taken ⇒ Time taken = Distance covered Speed Time taken = 14 , 90 , 00 , 000 3 × 10 5 = 496 . 7 s If sun stops giving out light now, we are able to see the sunlight for 496 . 7 s , since it takes this much time to reach our earth.

A bus takes 15 hours to travel from town X and Y and 12 hours to travel from town Y to Z. Calculate the speed of the bus from town 'X' to town 'Y'.

Given that, Distance from X to Y is = 700 km Time taken by the bus from X to Y is = 15 hours = 15 h We know that, Speed = Distance travelled time taken = 700 15 = 46 . 67 km h - 1 Speed of the bus from town 'X' to town 'Y' is 46 . 67 km h - 1 .

A bus takes 15 hours to travel from town X to town Y and 12 hours to travel from town Y to Z. Is the speed of the bus increasing or decreasing from town 'Y' to 'Z' as compared to the speed from 'X' to 'Y'? Find out.

Given that, Distance from town 'X' to town 'Y' is = 700 km Distance from town 'Y to town 'Z' is = 520 km Time taken by the bus from X to Y is = 15 hours = 15 h Time taken by the bus from Y to Z is = 12 hours = 12 h We know that, Speed = Distance travelled Time taken Speed of the bus from town 'X' to town 'Y' is = 700 15 = 46 . 67 km h - 1 . Similarly, speed of the bus from town 'Y' to town 'Z' is = 520 12 = 43 . 3 km h - 1 . Therefore, speed of the bus is decreasing, when it is traveling from town 'Y' to town 'Z'.

A bus takes 15 hours to travel from town X to town Y and 12 hours to travel from town Y to Z. What is the average speed of the bus throughout journey?

Given that, Total distance from town 'X' to town 'Y' and town 'Y to town 'Z' is = 700 km + 520 km = 1220 km Total time taken by the bus from X to Y and Y to Z is = 15 hours + 12 hours = 15 h + 12 h = 27 h We know that, Average speed = Total distance travelled Total time taken = 1220 27 = 45 . 2 km h - 1

Look at the diagram of a simple pendulum. The bob of the pendulum is released at point 'X'. The period of the oscillation is found to be 0 . 25 s . State one measure you can take to ensure that the measurement of the time period of the pendulum is as accurate as possible.

The measurement of the time period of the simple pendulum will be accurate when it oscillates in a vertical plane only. If it is tilted then the oscillations of the pendulum will be affected. While measuring time period start time from the extreme position, because at extreme positions bob of the pendulum momentarily stops.