Thursday , March 28 2024
Time and Motion

9th Class (CBSE) Science: Motion

Question: With the help of graph, show the uniform acceleration and uniform retardation of a body.

Answer:

OA and CB uniform acceleration

OA – shows uniform acceleration.

CB – shows uniform retardation.

Question: What conclusion do you draw about acceleration of the particle in motion from given velocity-time graph?

No acceleration and Uniform acceleration

Answer: (a) No acceleration, (b) Uniform acceleration

Question: A car accelerates uniformly from 20 km/h to 35 km/h in 5 s. Calculate (i) the acceleration and (ii) the distance covered by the car in that time.

Answer:

A car accelerates uniformly from 20 km - 35 km

Question: The odometer of a car reads 1800 km at the start of a trip and 2400 km at the end of the trip. If the trip took 10 h. Calculate the average speed of the car in km/h and m/s.

Answer: Distance covered by the car
s = 2400 – 1800 = 600 km.
Trip time = 10 hr
Average speed = ?

(i) Vav = 600 km.
(ii) In m/s (60 km/h) = 60 × 1000/60 × 60 = 16.6 m/s.

The average speed of the car in km/h = 60 km/h and in m/s is 16.6 m/s.

Question: An object travels 16 m in 4 s and then another 16 m in 3 s. What is the average speed of the object?

Answer: Total distance traveled by the object = 16 m + 16 m
= 32 m
Total time taken = 4 s + 3 s = 7
∴ Average speed = Total distance traveled/Total time taken
= 32/7 = 4.57 m/s.
∴ The average speed of the object is 4.57 m/s.

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