Questions Discussion for class 9th (lec 11)

video lectures for questions Discussion Lecture

Question 1: Calculate the time of flight of a body that is thrown up to a height of `5m` from the ground.

a) `1s`

b) `2s`

c) `2.5s`

d) `0.5s`

Question 2: A body travels in a semi-circular path of radius `7 m` as

shown. If the time taken to travel from `A` to `C` is `11 s`,

Find

(1) the distance covered.

(2) the displacement.

(3) the speed.

(4) velocity.

(5) What is the displacement if it completes the circle?

a) `22 m`,  `14 m`,  `2ms^{-1}`,  `1.27ms^{-1}`,  `Zero`.

b) `14 m`,  `22 m`,   `2ms^{-1}`,  `1.27ms^{-1}`,  `Zero`.

c) `14 m`,  `22 m`,   `2ms^{1}`,  `1.27ms^{-1}`,  `14 m`.

d) `14 m`,  `22 m`,   `1..27ms^{-1}`, `2ms^{-1}`,  `14 m`.

Question 3: A particle moves from `P` to `Q` with a uniform velocity `v_{1}` and `Q` to `P` with a velocity `v_{2}`. If it moves along a straight line between `P` and `Q`, then its average velocity will be ______.

a) `\frac{2v_{1}v_{2}}{v_{1}+v_{2}}`

b) `\frac{v_{1}v_{2}}{2}`

c) `\frac{v_{1}+v_{2}}{2}`

d) `zero`

Question 4: If a body travels with an acceleration `a_{1}` for time `t_{1}` and acceleration `a{2}` for time `t_{2}`, `t_{1}` and `t_{2}` being successive time intervals, then the average acceleration of the body is 

a) `\frac{a_{1}t_{1}+a_{2}t_{2}}{2(t_{1}+t_{2})}`

b) `\frac{a_{1}t_{1}+a_{2}t_{2}}{(t_{1}+t_{2})}`

c) `\frac{a_{1}+a_{2}}{(t_{1}+t_{2})}`

d) `\frac{a_{1}t_{1}-a_{2}t_{2}}{(t_{1}+t_{2})}`

Question 5: If a body covers `26 m` and `30 m` in the `6th` and `7th` seconds of its travel, then the initial velocity and acceleration of the body are

(a) `4ms^{-1}`, `4ms^{-2}`  

(b) `6ms^{-1}`, `4ms^{-2}`  

(c) `10 ms^{-1}`, `8 ms^{-2}`  

(d) `0`, `4ms^{-2}`

Question 6: In the given figure, determine the force acting along x-axis if the angle between the force and x-axis is `q = 30°` or `60°`.

a) `F_{x}`=`15cos\theta`

b) `F_{x}`=`15sin\theta`

c) `F_{x}`=`30cos\theta`

d) `F_{x}`=`30sin\theta`

Question 7: A person travels 6 m towards east, `8 m` towards north and `16 m` towards south. What is the displacement of the person?

a) `12 m`

b) `16 m`

c) `8 m`

d) `10 m`

Question 8: The velocity of a retarding body changes from `90kmh^{-1}` to `36kmh^{-1}`. Find the change in its velocity in `ms^{-1}`.

a) `15ms^{-1}`

b) `15ms`

c) `-15ms^{-1}`

d) `-15ms`

Question 9: An object travels for `10 s` with uniform acceleration along a straight line path. During this period if the velocity of the object is increased from `5ms^{-1}` to `25ms^{-1}`, then find the distance traveled by the body.

a) `150 m`

b) `125 m`

c) `250 m`

d) `50 m`

Question 10: A body is projected vertically upward. If its velocity after `2 s` is `25ms^{-1}`, find the velocity of projection. (Take `g` = `10 ms^{-2}`) 

a) `45 ms`

b) `40ms^{-1}`

c) `50ms^{-1}`

d) `45ms^{-1}`

Question 11: A stone is projected vertically upward with a velocity of `25ms^{-1}`. Find its time of descent.

(Take `g` = `10 ms^{-2}`) 

a) `2.5s`

b) `25 s`

c) `10s`

d) `0.25s`

Question 12: Calculate the time of flight of a body which is thrown upto a height of `5 m` from the ground.

a) `2.5s`

b) `0.5s`

c) `1s`

d) `2s`

Question  13: A body projected vertically up crosses points `A` and `B` separated by `28 m` with velocities one-third and onefourth of the initial velocity, respectively. What is the maximum height reached by it above the ground?

a) `576 m`

b) `288 m`

c) `365 m`

d) `456 m`

Question 14: A  person travels the total distance in two parts in the ratio `2 : 1` with a constant speed of `30kmh^{-1}` in the first part and `40kmh^{-1}` in the second part. What is the average speed of the journey?

a) `32.73kmh^{-1}`

b) `30kmh^{-1}`

c) `43.73kmh^{-1}`

d) `40kmh^{-1}`

Question 15: An athlete one round of a circular track of diameter `200 m` in `40s`. What is the distance he will cover after `2 min` `20s` and what will be his displacement?

a) `2200 m`

b) `100 m`

c) `200 m`

d) `4400 m`

Question 16: joseph jogging on a `300 m` straight path reaches from one end `A` to the other end `B`  in `2 min` `50s` and turns around and reaches point `C` `100 m` back in `1 min`. What will be joseph’s average speed and average velocity from end `A` to end `C` ?

a) `1.73ms^{-1}` ,`0.87ms^{-1}`

b) `1.73ms` , `0.87ms^{-1}`

c) `1.73ms^{-1}` , `0.87ms`

d) `1.73ms` , `0.87 ms`

Question 17: Abdul while going to school by car find the average speed to be `20kmh^{-1}`. At of returning on the same route, there was less crowd and the average speed was `40kmh^{-1}`. What is the average speed of Abdul in this whole journey?

a) `26.67kmh^{-1}`

b) `60.6kmh`

c) `20.76kmh^{-1}`

d) `20.67kmh^{-1}`

Question 18: A motor boat from rest in a lake moves along a straight line with a constant acceleration of `3.0ms^{-1}` for `8.0 s`. What is the distance covered by the motorboat in this time interval? 

a) `64 m` 

b) `96 m`

c) `89 m`

d) `54 m`

Question 19: A ball is dropped from a height of `20 m`. If its velocity increases at the same rate of uniform acceleration of `10ms^{-2}`, what velocity will it hit the ground? After how much time will it hit the ground?

a) `1 s`

b) `0.5s`

c) `1.5s`

d) `2s`

Question 20:  An artificial satellite is moving in a circular orbit of radius `42250 km`. If it revolves around the earth in `24 hours`, calculate its speed.

a) `0.5kms^{-1}`

b) `2kms^{-1}`

c) `2.07 kms^{-1}`

d) `3.07kms^{-1}`

Direction for questions `21` to `27`

State whether the following statements are true or 

false.

Question 21: A body moves with retardation when it is projected vertically upwards.

Question 22: A body is projected vertically up. On reaching maximum height, its velocity becomes zero.

Question 23: Velocity-time graph can be used to find the displacement. Question 24: If a body moves with constant velocity, its displacement depends on the square of time taken. Question 25: When two balls of different masses are thrown vertically upwards with the same initial speed, the heavier body rises to greater height than the lighter body. Question 26: Equations of motion are applicable only when a body moves with uniform velocity. Question 27: The distance traveled by a freely falling body in every successive second is the same.

Direction for questions `28` to `33` 

Fill in the blanks.

Question 28: The ratio of velocities acquired by a freely falling body starting from rest at the end of `1 second` and `2 seconds` is ________. 

Question 29: If a stone is thrown vertically up and it is caught after time `‘t’ seconds`, then the maximum height reached by it is ________. 

Question 30: Area under the velocity–time graph gives ________. 

Question 31:  The ratio of magnitude of average velocity to average speed is ________. 

Question 32:  The directions of both displacement and average velocity are ________. 

Question 33: ____________ is produced in a body whenever there is a change in its velocity.

Direction for question `34`

Match the entries in Column `A` with the appropriate 

ones in Column `B`.

Answer key

Q1 (b), Q2 (a), Q3 (d), Q4 (b), Q5 (a), Q6 (a), Q7 (d), Q8 (c), Q9 (a), Q10 (d), Q11 (a), Q12 (d), Q13 (a), Q14 (a), Q15 (c), Q16 (a), Q17 (d), Q18 (b), Q19 (d), Q20 (d)

Q21 - True , Q22 - True , Q23- True , Q24- False , Q25- False , Q26- False , Q27- False

Q28- `1:2` , Q29- `g\frac{t^{2}}{8}` ,  Q30- Displacement , Q31- Less than or equal to 1, Q32-Same, Q33-Acceleration

Q34:  A : c     B : d     C : f and d     D : g     E : b     F : h     G : a     H : e