Assignment - Motion, Class 9, Science PDF Download

TRUE OR FALSE

1. The motion in animals is called locomotion. Mechanics deals with the motion of non living object.
2. Kinematics deals with the motion of non-living object without taking into account the cause of their motion.
3. Motion along a curved line is called translatory or rectilinear motion.
4. A body is said to be at rest if it does not change its position with respect to the reference point.
5. A quantity which can be represented completely by magnitude along is called a vector quantity.
6. A quantity which can be completely specified by magnitude as well as direction is called a scalar quantity.
7. Velocity and speed are measured in different units.
8. In one dimensional motion the average velocity and the instantaneous velocity are unequal.
9. A motion is said to be uniform if a body undergoes equal displacements in equal intervals of time.
10. A motion is said to be uniform if x α t2.
11. Acceleration is defined as the rate of change of velocity.
12. The graph between velocity and time for uniform acceleration is a curved line.

MATCH THE COLUMN

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2. 

FILL IN THE BLANKS

1. Mechanics is the branch of physics which deals with ..........................
2. Statics is a sub branch of mechanics which deals with bodies at ..........................
3. Dynamics is a sub branch of mechanics which deals with bodies in ..........................
4. A point object is one whose size is .......................... as compared to the distance it moves.
5. A body is said to be at rest if it does not change its .......................... with respect to the surroundings.
6. A body is said to be in motion if it change its .......................... with respect to the surroundings.
7. The reference point from which the distance of a body is measured is called ..........................
8. Distance is the .......................... path followed by a body between two points.
9. Displacement is the .......................... distance between two points.
10. A quantity which can be completely represented by magnitude alone is called ..........................
11. A quantity which can be completely represented by magnitude and direction is called ..........................
12. Speed is the ratio of the .......................... travelled to the time taken. 

SHORT ANSWER TYPE QUESTIONS

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

[Ans. 16/3  ms^–1]

•  A train starting from a railway station and moving with uniform acceleration attains a speed of 40 km/h^–1 in 10 minutes. Find its acceleration –

[Ans. 240 km/h2]

• What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis?

[Ans. at rest.]

•  A racing car has a uniform acceleration of 40 m/s2 what distance will it cover in 10s after start?

[Ans. 2000 m.]

• Name the quantity that essentially changes as a body moves.

[Ans. Time]

• What does the area below v – t graph give?

[Ans. Displacement]

• Relate 36 km/h with m/s.

[Ans. 10 m/s]

• A car travels   of a circle with radius r. Find the ratio of the distance to it's displacement. 

[Ans. ]

• If 5 m/s and 10 m/s are the velocities of a body having a uniform acceleration in same time interval. What will be its average velocity?

[Ans. 7.5 m/s]

• What is the nature of motion of two cars A and B as depicted by the v–t graph in fig –

[Ans. A – Uniform motion, B – Uniform acceleration]

• . When a body moving with a speed of 20 m/s. stops in 20 seconds, what is the acceleration?

[Ans –1 m/s²]

• A particle moves 3m north, then 4m east and finally 6m south calculate its distance travelled and displacement

[Ans 13m, 5m]

•  A car travels 30km at a uniform speed of 40 km/h and the next 30km at a uniform speed of 20km/h. Find its average speed

[26.7 km/h]

• Ravina takes 20 minutes to cover a distance of 3.2 kilometres on a bicycle. Calculate her speed in units of kilometre/minute, metre/minute, kilometre/hour. and m/s.

[0.16 km/min, 160m/min, 9.6 km/h, 2.67m/s]

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

Ans. 1/5 m / s² , –2/5 m / s²

• The velocity of a car is 18m/s. Express this velocity in km/h.

[64.8 km/h]

•  An electric train is moving with a velocity of 120 km/h. How much distance will it cover in 30 second?

[1km]

• A train starting from rest attains a velocity of 72 km/h in 5 minutes. Assuming that the acceleration is uniform, find (i) the acceleration and (ii) the distance travelled by the train for attaining this velocity –

Ans. (i) 1/ 15 m/s² (ii) 3 km.

•  A bus covers 30km with a uniform speed of 60 km/h and the next 30km with a uniform speed of 40km/h. Find the total time taken and the average speed.

[Ans. 75minutes, 48 km/h]

• A car moves 30 minute with a uniform speed of 30km/h and next 30 minute moves with uniform speed of 60 km/h. Find the average speed in entire journey.

[Ans. 45 km/h]

• A 60m long train moving on a staright level track passes a pole in 5s, find (a) the speed of train (b) the time it will take to cross a 540 m long bridge.

[Ans. 12m/s, 50s]

• The brakes applied to a car it produce an acceleration of –10 m/s2. If the car takes 5s to stop after applying the brakes, calculate the distance covered by the car before coming to rest.

[Ans. 125m]

• What is the direction of velocity in a circular motion?

[Ans. tangent at any point]

• Is it possible to have the speed of a moving body zero ?

[Ans. No.]

• If two bodies in circular paths of radii 1:2 take same time to complete their circles, what is the ratio of their angular speeds ?

[Ans. 1 : 2]

• Is the x–t graph given in the figure valid. Why? 
• 

[Ans. Not possible]

• When a moving car returns to the same point what will be the displacement –

[Ans. Zero]

• A body moving with a constant speed, say 10 m/s on a frictionless surface has uniform motion while a freely falling object has non uniform motion. Give reason –

[Ans. Due to presence of acceleration due to gravity falling object accelerates.]

• A 150 m long train crosses a bridge of length 250 m in 25 seconds. What is its velocity?

[Ans. 16 m/s]

• A ship is moving at a speed of 56 km/h. One second later it is moving at 58 km/h. What is its acceleration?

[Ans. 59 m/ s² ]

• If a car starts from rest and attains speed 20 m/s in 25 seconds. Find the acceleration.

[Ans. a = 45 m/s²]

• How much time will it take for a body with acceleration 2 m/s2, to gain a velocity of 10 m/s, starting from rest?

[Ans. 5 sec]

• When the slope of v–t graph is negative and constant, what is the nature of acceleration?

[Ans. deaccelerates , zero.]