The earth takes one year to orbit the Sun at a distance of 1 . 5 × 10 11 m . Calculate the speed. Explain why this is its average speed and not its velocity.

Given the distance between the sun and the earth r = 1 . 5 × 10 11 m . The time of taking one complete orbit = T = 1 year = 365 × 24 × 60 × 60 = 31536000 = 3 . 1536 × 10 7 sec . Let us suppose the earth orbits the sun in a circular orbit the length of the path will be the circumference of the circle having its radius equal to the distance between the earth and the sun. The path length is 2 πr = 2 × 3 . 14 × 1 . 5 × 10 11 m = 9 . 4 × 10 11 m . The speed of the earth s = distance time = 9 . 4 × 10 11 3 . 1536 × 10 7 = 3 × 10 4 ms - 1 = 30 kms - 1 It is the average speed. Since the earth returns to its initial position after one year, the displacement of the earth is zero. Therefore, the average velocity of the earth during one year is also zero.

The Table shows the displacement of a racing car at different times as it travels along a straight track during a speed trial. Displacement / m 0 85 170 255 340 Time / s 0 1 . 0 2 . 0 3 . 0 4 . 0 Draw the displacement-time graph and use it to find the car's velocity.

The graph between the displacement(distance and the time is shown above. From the graph, we can take any value of time and the corresponding distance covered by the car in that time. From the graph, we have the velocity = distance time = slope of V - T graph For example, the distance covered in time 2 sec is 170 m . Therefore, the slope of the graph 170 m 2 sec . = 85 m / sec

An old car travels due south.The distance it travels at hourly intervals is shown in the table Time / h 0 1 2 3 4 Distance / km 0 23 46 69 84 From the distance-time graph deduce the car's speed in kmh - 1 during the first three hours of the journey

The given data Time / h 0 1 2 3 4 Distance / km 0 23 46 69 84 Using the above data the graph is as follows. The time is taken on X - axis The distance is taken on y - axis From the graph it is evident that the distance travelled by the car during first three hours is 69 km . Therefore, the car's speed during this period= s = distance travelled time taken = 69 3 = 23 kmh - 1

An old car travels due south. The distance it travels at hourly intervals is shown in the table Time / h 0 1 2 3 4 Distance / km 0 23 46 69 84 What is the car's average speed in kmh - 1 during the whole journey,

The given data Time / h 0 1 2 3 4 Distance / km 0 23 46 69 84 Using the above data the graph is as follows. The time is taken on X - axis The distance is taken on y - axis From the graph it is evident that the distance travelled by the car during total journey= 84 km Therefore, the car's speed during this period= s = distance travelled time taken = 84 4 = 21 kmh - 1

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A submarine uses sonar to measure the depth of water below it. Reflected sound waves are detected $0.40 s$ after they were transmitted. How deep is the water.? Speed of sound in water= $1500 {ms}^{- 1}$

Important Questions on Kinematics: Describing Motion

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AS and A Level

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 9

The earth takes one year to orbitthe Sun at a distance of $1.5 \times 10^{11} m$ . Calculate the speed. Explain why this is its average speed and not its velocity.

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AS and A Level

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 10

The displacement-time sketch graph in th figure represent the journey of a bus. What does the graph tell you about the journey?

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 11

Sketch a displacement - time graph to show your motion for the following event. You are walking at aconstant speed across a field after jumping off a gate, Suddenly you see a horse and stop. Your friend says there's no danger, so you walk on at a reduced constant speed. The horse neigh, and you run back to the gate. Explain how each section of the walk relates to a section of your graph.

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 12

The Table shows the displacement of a racing car at different times as it travels along a straight track during a speed trial. Determine the car’s velocity.

Displacement $/ m$	$0$	$85$	$170$	$255$	$340$
Time $/ s$	$0$	$1.0$	$2.0$	$3.0$	$4.0$

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 12

The Table shows the displacement of a racing car at different times as it travels along a straight track during a speed trial.

Displacement $/ m$	$0$	$85$	$170$	$255$	$340$
Time $/ s$	$0$	$1.0$	$2.0$	$3.0$	$4.0$

Draw the displacement-time graph and use it to find the car's velocity.

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AS and A Level

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 13

An old car travels due south. The distance it travels at hourly intervals is shown in the table

Draw the distance-time graph to represent the car journey.

Time $/ h$	$0$	$1$	$2$	$3$	$4$
Distance $/ km$	$0$	$23$	$46$	$69$	$84$

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AS and A Level

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Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 13

An old car travels due south.The distance it travels at hourly intervals is shown in the table

Time / h	0	1	2	3	4
Distance / km	0	23	46	69	84

From the distance-time graph deduce the car's speed in ${kmh}^{- 1}$ during the first three hours of the journey

MEDIUM

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 1 - Kinematics: Describing Motion>Questions>Q 13

An old car travels due south. The distance it travels at hourly intervals is shown in the table

Time / h	0	1	2	3	4
Distance / km	0	23	46	69	84

What is the car's average speed in ${kmh}^{- 1}$ during the whole journey,

A submarine uses sonar to measure the depth of water below it. Reflected sound waves are detected 0.40 s after they were transmitted. How deep is the water.? Speed of sound in water=1500 ms-1

Important Questions on Kinematics: Describing Motion

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A submarine uses sonar to measure the depth of water below it. Reflected sound waves are detected $0.40 s$ after they were transmitted. How deep is the water.? Speed of sound in water= $1500 {ms}^{- 1}$