Motion and Time

We judge whether an object moves fast or slow by the distance it covers in a given time. Speed is the distance covered per unit time, so speed = distance / time, and its basic unit is metre per second (m/s), though km/h is used for vehicles. An object moving along a straight line at constant speed is in uniform motion, while one whose speed keeps changing is in non-uniform motion. Usually we calculate the average speed, total distance divided by total time. Time was once measured with sundials, sand clocks and water clocks; modern clocks rely on periodic motion. A simple pendulum, a small bob hung by a thread, swings back and forth, and the time for one oscillation is its time period, which stays the same for a given length. A speedometer shows speed in km/h, and an odometer shows the distance travelled. Motion can also be shown by a distance-time graph, which is a straight line for uniform motion.

Detailed Worksheet: Motion and Time Section A - Definitions (10 marks) 1. Define speed. Write its formula and SI unit. (2 marks) 2. Distinguish between uniform and non-uniform motion with an example of each. (2 marks) 3. What is a simple pendulum? Define one oscillation. (2 marks) 4. What is the time period of a pendulum? Does it change for a pendulum of fixed length? (2 marks) 5. What do a speedometer and an odometer measure? (2 marks) Section B - Calculations and Applications (15 marks) 6. A car covers 150 km in 3 hours. (i) Find its speed in km/h. (ii) How far will it go in 5 hours at the same speed? (iii) How long will it take to cover 400 km? (3 marks) 7. A pendulum makes 20 oscillations in 32 seconds. (i) Find its time period. (ii) How many oscillations will it make in 48 seconds? (iii) How long will 50 oscillations take? (3 marks) 8. Convert: (i) 36 km/h into m/s (ii) 15 m/s into km/h (iii) 90 km/h into m/s. (3 marks) 9. Salma takes 15 minutes from her house to reach her school on a bicycle at 2 m/s. Find the distance between her house and school in metres and in km. (3 marks) 10. The odometer of a car read 57321.0 km when the clock showed 08:30 am. At 08:50 am it read 57336.0 km. (i) Find the distance moved. (ii) Find the speed in km/min. (iii) Find the speed in km/h. (3 marks) Section C - Diagrams (10 marks) 11. Draw a distance-time graph for a bus: time (min) 0, 2, 4, 6, 8, 10; distance (km) 0, 1, 2, 3, 4, 5. What kind of motion is it? Find its speed. (4 marks) 12. Draw a labelled diagram of a simple pendulum showing the bob, thread, stand, mean position and extreme positions. (3 marks) 13. Draw labelled sketches of any two ancient time-measuring devices: a sundial, a sand clock or a water clock. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Two cars A and B start together. A covers 120 km in 2 hours and B covers 180 km in 4 hours. (i) Find the speed of each. (ii) Which is faster? (iii) How far apart will they be after 2 hours if they move in the same direction? (iv) Draw rough distance-time graphs of both on the same axes in words, saying which line is steeper. (5 marks) 15. A train travels 60 km in the first hour, 40 km in the second hour and 80 km in the third hour. (i) Is its motion uniform? (ii) Find its average speed. (iii) Where would a passenger see the speed at any instant? (iv) Why is non-uniform motion more common in daily life? (5 marks) 16. Paheli and Boojho made pendulums of lengths 50 cm and 100 cm. (i) Whose pendulum will have a longer time period? (ii) How would they measure the time period accurately? (iii) Why should they count 20 oscillations rather than 1? (iv) Name one use of the periodic motion of a pendulum. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Write units with every answer and convert units before calculating.