Q1. An object has moved through a distance. Can it have zero displacement? Give examples if yes?

Q2. When will you say a body is in (a) uniform acceleration; (b) non-uniform acceleration

Nikhil

NCERT Neumericals

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» Manava Bharati School, New Delhi-Class IX / Physics Classroom lessons
» NCERT Neumericals

Q1. An object has moved through a distance. Can it have zero displacement? Give examples if yes?

Q2. When will you say a body is in (a) uniform acceleration; (b) non-uniform acceleration

Nikhil

Ans1- yes an object has moved through a distance can have displacement zero but only on a straight line . for example i walked a distance of 1km from point a to b ,where a and b are straight path.

Ans2- (a) a body is said to be uniform acceleration when a body covers equal distance in equal intervals of time.

- (b) a body is said to be uniform acceleration when a body covers unequal distance in equal intervals of time.

Ankur Sharma

IX B

Ankur,

(a)….have a re-think!! Something wrong with your statement "but only on a straight line." I give you time to think.

(b)… "equal distance in equal intervals of time"…..would mean constant velocity!! But we are talking about acceleration??

……."when a body covers unequal distance in equal intervals of time"….that is acceleration by itself!! We have to think about non-uniform acceleration?

Nikhil

sir can the displacement be 0 in circular motion

class-ix-c

pallavi sharma

(b) I will think and come back to you

Ans1-Yes we can have zero displacement, suppose i start walking from point A and after completing 1 round I reach the same place that is I had travel zero displacement.

Anandita Dalal

ix-c

ans1) Anandita there can be another way also :-

a body starts at A and covers 5 m to reach B in 5 sec. It again come back to A in same time.so,during this motion

time= 5+5 =10 sec

displacement=0 (because the initial and the final position is the same)

pankaj jha

ix-c

PANKAJ

IX-C

ans 2 ) if an object travels in a straight line and ist velocity increases or decreases by equal amount in equal intervals of time, then the body is siad to be

in uniform acceleration

if an object travels in a straight line and ist velocity increases or decreases by unequal amount in equal intervals of time, then the body is siad to be

in uniform acceleration

PANKAJ

IX-C

Ans2- (i) A body is said to have uniform acceieration if it travels in a stright path in such a way that its uniform rate i.e., the velocity of a body increases or decreases by equal amounts in an equal interval of time.

(ii) Abody is said to have non-uniform acceleration if it travels in a stright path in such a way that its velocity changes at a non-uniform rate, i.e., the velocity of a body increases or decreases in unequal amounnts in an equal interval of time.

Anandita Dalal

ix-c

(becuse its initial position and final position are same.

in this case the displacement is zero .(because its initial and final position are same.

i have some more questions so i am giving to you

Q1. a sound is heard 5seconds later than the lightning is seen in the sky on a rainy day. find the distance of location of lightning. given speed of sound=346m/s

Q2.a taxi driver noted the reading on odometer as1052km when he started the journey after 30 minutes drive odometer reading was 1088km find the average speed of the taxi

Q3in a long distance race athletes were expected to take 4rounds of the circular track of diameter 28m calculate

the total distance travelled and displacement at the end of race

Q4.a bus starts from rest and attains a speed of 36km/hr in 10 minutes while moving with uniform acceleration calculate the acceleration of the bus

Q5.a car is travelling with a speed of 36km hr-1 the driver applies break and retards the car uniformly the car is stopped in 5seconds find-(1)retardation of the car (2) distance travelled before it stops

Q6. a car is retarded by applying brakes at the rate of 2ms-2 it is finally stopped in 10 seconds find its initial velocity

Q7. a ship is moving at a speed of 56km/hr one second later it is moving at 58km/hr what is its acceleration

Q8. brakes applied to a car produce a uniform retardation of 90cm/ s2 if the car was travelling with a velocity of 27m/s then what distance will it cover before coming to rest?

Q9. calculate the speed of tip of seconds hand of a watch of length 1.5cm

Q10. a bullet is fired on a wall with a velocity of 100m/s if the bullet stops at the depth of 10 cm inside the wall then find the retardation produced by the wall

Q11. a car accelerates uniformly from 27km/h to 45km/hr in 2 seconds calculate (1) acceleration (2) distance covered by car

Q12. on a 120 km track a train travels the first 30 km at a uniform rate speed of 30km/hr how fast must the train travel the next 90km so as to average 60km/hr for entire trip?

Q13. a car travels 30 km at a uniform speed of 60km/hr and next30 km at a uniform speed of 20km/hr find its average speed

Q14. a train acquires a velocity of 36km/hr in 10 seconds just after the start it takes 20seconds to stop calculate the acceleration in the two cases

Q15. a ball is gently dropped from a hieght of 20m if its velocity increase uniformly at the rate of 10ms-2 with what velocity will it strike the ground ? after what time will it strike rhe ground?

Solution 1-

Let us take the example of an athlete running in a 100m race, after completing one round of the ground it will again reach the the starting point so it will have zero displacement. But, the distance covered by the athlete will be the circumference of the ground i.e. 100m.

Another example can be of a student going to his school and then returning back . In this case the distance traveled will twice the distance from his home to school but, the displacement will be 0 as he's back to his home.

Solution 2-

(a) A body can be said to be in uniform acceleration when its change in velocity is uniform for every time interval of its motion. This means that the slope of velocity-time graph will be a straight line.

(b) A body can be said to be in non-uniform acceleration when its change in velocity is not uniform for every time interval of its motion. This means that the slope of velocity-time graph is not a straight line instead it is in the shape of a curve or zig-zag or something like that.

I am not be able to do 1 question of ncert book of chapter motion on page 112 ques no 5. plz help me out,

**QUES**. A driver of a car travelling at 52m/h applies the brakes and accelerates uniformly in the opposite direction. The stops in 5sec. Another driver going at 3km/h in another car applies his brakes slowly and stops in 10sec. On the same graph paper, plot the speed versus time graphs for the two cars. which of the two cars travelled farther after the brakes were apllied?

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