Motion Class 9 Worksheet Science Chapter 7

Q.1. Fill in the blanks:

(i) The branch of Physics, which deals with the behaviour of moving objects, is known as Mechanics.
(ii) An object is said to be in motiom if it changes its position with respect to its surroundings in a given time.
(iii) A Frame of reference is another object of scene with respect to which we compare an object's position.
(iv) The distance time graph for Uniform motion is a straight line.
(v) A non uniform motion is also called an accelerated motion.

Q.2. The numerical ratio of displacement to distance for a moving object is: 
(a) Always less than 1
(b) Equal to 1 or more than 1
(c) Always more than 1
(d) Equal to 1 or less than 1

Correct Answer is Option (d)

Q.3. A boy is sitting on a merry-go-round which is moving with a constant speed of 10 m S–1. This means that the boy is:
(a) At rest
(b) Moving with no acceleration
(c) In accelerated motion
(d) Moving with uniform velocity

Correct Answer is Option (c)

Q.4. In which of the following cases of motion, the distance moved and the magnitude of displacement are equal ? 
(a) If the car is moving on straight road
(b) If the car is moving on circular road
(c) If the pendulum is moving to and fro
(d) If a planet is moving around the sun

Correct Answer is Option (a)

Q.5. The speed of a moving object is determined to be 0.06 m/s. this speed is equal to:
(a) 2.16 km/h
(b) 1.08 km/h
(c) 0.216 km/h
(d) 0.0216 km/h

Correct Answer is Option (c)

Q.6. Is displacement a scalar quantity?

Displacement is a vector quantity and its units are meter, kilometer etc.

Q.7. State whether distance is a scalar or a vector quantity.

Distance is a scalar quantity and its units are meter, kilometer etc 

Q.8. Give one example of a situation in which a body has a certain average speed but its average velocity is zero.

Movement around a circular track. In this case the displacement after one complete round is zero hence velocity will be zero.

Q.9. Which of the two can be zero under certain conditions: average speed of a moving body or average velocity of a moving body?

Average velocity. If displacement of a body is zero then its average velocity will be zero.

Q.10. What does the path of an object look like when it is in uniform motion?

Graphically the path of an object will be linear i.e. look like a straight line when it is in uniform motion.

Q.11. Distinguish between speed and velocity.

Speed of a body is the distance travelled by it per unit time while velocity is displacement per unit time of the body during movement.

Q.12. An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.

Yes, if an object has moved through a distance it can have zero displacement because displacement of an object is the actual change in its position when it moves from one position to the other. So if an object travels from point A to B and then returns back to point A again, the total displacement is zero.

Q.13. State which of the following situations are possible and give an example for each of these: 
(a) an object with a constant acceleration but with zero velocity 
(b) an object moving in a certain direction with an acceleration in the perpendicular direction.

(a) An object with a constant acceleration can still have the zero velocity. For example, an object which is at rest on the surface of earth will have zero velocity but still being acted upon by the gravitational force of earth with an acceleration of 9.81 ms^-2 towards the center of earth. Hence when an object starts falling freely can have constant acceleration but with zero velocity.
(b) When an athlete moves with a velocity of constant magnitude along the circular path, the only change in his velocity is due to the change in the direction of motion. Here, the motion of the athlete moving along a circular path is, therefore, an example of an accelerated motion where acceleration is always perpendicular to direction of motion of an object at a given instance. Hence it is possible when an object moves on a circular path.

Q.14. A train starting from rest moves with a uniform acceleration of 0.2 m/s² for 5 minutes. Calculate the speed acquired and the distance travelled in this time.

V = u + at & S = ut + ½ at²
U = 0, v = ?
a = 0.2 m/s²
t = 300 sec
v = 0 + .2 x 300 = 60 m/s
By putting the values in the second equation of motion the distance can be calculated.
S = 0 + ½ × 0.2 × 300 × 300 = 9000 m or 9 km

Q.15. State an important characteristic of uniform circular motion. Name the force which brings about uniform circular motion.

An important characteristic of uniform circular motion is that the direction of motion in it changes continuously with time, so it is accelerated. Centripetal force brings about uniform circular motion.