Motion in one dimension Extra Questions Class 9

Motion in one dimension | Extra Questions | Class 9

Q1. Differentiate between scalar and vector quantities, giving two examples of each.

Ans:

Scalar quantityVector quantity
It is a physical quantity that is expressed only by its magnitude.It is a physical quantity that requires magnitude as well as direction to express it.
Example – mass, lengthExample – velocity, displacement

Q2. When is the magnitude of displacement equal to the distance?

Ans: The magnitude of displacement equals the distance if a body moves in one particular direction or along a straight line.

Q3. Which of the quantity speed or velocity gives the direction of motion of a body?

Ans: The velocity of a body gives the direction of motion.

Q4. Distinguish between speed and velocity.

Ans:

VelocitySpeed
The velocity of an object is the rate at which an object changes position in a certain direction.The rate at which an object covers a certain distance is the speed of the object.
It is a vector quantityIt is a scalar quantity
It can be zero, negative, or positive.It can never be negative or zero.

Q5. Give an example of the motion of a body moving with a constant speed but with a variable velocity. Draw a diagram to represent such a motion.

Ans: A body in uniform circular motion has a constant speed, but the velocity varies as the direction of the velocity changes continuously.

Motion in one dimension | Extra Questions | Class 9

Q6. Define acceleration. State its unit.

Ans: The rate of change of velocity of an object is called its acceleration.

Its unit is m/s2

Q. Arrange the following speeds in increasing order 10 m/s, 1 km/min and 18 km/h.

Q7. A car travels the first 30 km with a uniform speed of 60 km/hr and the next 30 km with a uniform speed of 40 km/hr.

Calculate:

i) the total time of the journey

ii) the average speed of the car

Q8. A train takes 2 h to reach station B from station A, and then 3 h to return from station B to station A. The distance between the two stations is 200 km. Find the:

i) the average speed

ii) the average velocity of the train.

Q9. A car is moving with a velocity of 20 m/s. The brakes are applied to retard it at a rate of 2 m/s2. What will be the velocity after 5 s of applying brakes?

Q10. A car is moving in a straight line with a speed of 18 km/h. It stopped in 5 s by applying the brakes.

Find:

i) speed of the car in m/s

ii) the retardation

iii) the speed of the car after 2 s of applying the brakes.

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