Question on motion for class 9

1. An object travels 16 m in 4 s and then another 16 m in 2 s. What is the average speed of the object?

[Ans. 5.33 m/s]

2. The odometer of a car reads 2000 km at the start of a trip and 2400 km at the end of the trip. If the trip took 8 h. calculate the average speed of the car in km/h and m/s.

[Ans. 50 km/h : 13.9 m/s)

3. Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. Find the average speed and average velocity of Usha.

[Ans. 3 m s^- 1 ; zero]

4. Starting from a stationary position, Rahul paddles his bicycle to attain a velocity of 6 m/s in 30 s. Then he applies brakes such that the velocity of bicycle comes down to 4 m/s in the next 5 s. Calculate the acceleration of the bicycle in both the cases.

[Ans. 0.2 m s^- 2 ; – 0.4m / (s ^ 2) ]

5. Ahmed is moving in his car with a velocity of 45 km/h. How much distance will he cover (a) in one minute and (b) in one second ?

[Ans. 750 m ; 12.5 m]

6. An electric train is moving with a velocity of 120 km/h. How much distance will it move in 30 s?

[Ans. 1000 m]

7. A body is moving with a velocity of 15 m/s. If the motion is uniform, what will be the velocity after 10 s ?

[Ans. 15 m/s]

8. A train travels some distance with a speed of 30 km/h and returns with a speed of 45 km/h. Calculate the average speed of the train.

[Ans. 36 km/h]

9. A train 100 m long moving on a straight level track passes a pole in 5 s. Find (a) the speed of the train (b) the time it will take to cross a bridge 500 m long.

[Ans. (a) 20 m/s (b) 30 s)

10. A car travels along a straight line for first half time with speed 40 km/h and the second half time with speed 60 km/h. Find the average speed of the car.

[Ans. 50 km/h]

11. A body starts rolling over a surface with an initial velocity of 0.5m / (s^2) . Due to friction, its velocity decreases at the rate of 0.5m / (s ^ 2) How much time will it take for to stop ?

[Ans. 10 s]

12. A car travelling at 36 km/h speeds up to 72 km/h in 5 seconds. What is its acceleration? If the same car stops in 20 seconds, what is the retardation?

(Ans. (2 m/(s^2)) ; – 1 m / (s ^ 2) ]