Speed and Velocity for class 9th (lec 6)

 video lectures for Speed and Velocity

 Question 1: The ratio of the magnitude of average velocity to average speed is ________.

a) `\frac{Displacement}{Distance}`

b) `\frac{Distance}{Displacement}`

c) `Distance\timesDisplacement`

d) `Displacement\timesDistance`

Question 2: If a body is projected vertically up from a point and it returns to the same point, its 

 

(a) average speed is zero, but not average velocity.

(b) Both average speed and average velocity are zero.  

(c) average velocity is zero but not average speed.  

(d) Both average speed and velocity depend upon the path.

Question 3: A vertically projected down body travels with

a)  uniform velocity.

b) uniform speed. 

c) uniform acceleration

d) uniform retardation.

Question 4: The velocity of a retarding body changes from `90 kmh^{-1}` to `36 kmh^{-1}`. Find the change in its velocity in `ms^{-1}`.

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

b) `15 ms^{-1}`

c)  `-18 ms^{-1}`

d) `10 ms^{-1}`

Question 5: A particle moves from `P` to `Q` with a uniform velocity `v_{1}` and `Q` to `P` with a velocity  `v_{2}`.

Its average velocity is _____________.

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

b) `v_{1}-v_{2}`

c) zero

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

Question 6: From the velocity-time graph given below, for a body projected vertically upwards,  find the velocity of projection

a) `20 ms^{-1}`

b) `10 ms^{-1}`

c) `-20 ms^{-1}`

d) `24 ms^{-1}`

Question 7: The distance traveled by a body in the nth second is given by the expression `(2 + 3n)`. find its velocity at the end of `2 sec`. 

a) `10 ms^{-1}`

b) `9 ms^{-1}`

c) `9.5 ms^{-1}`

d) `10.5 ms^{-1}`

Question 8: What is the average velocity of a car that moved `60 km` in `3 hours`.

a) `30 kmh^{-1}`

b) `60 kmh^{-1}`

c) `20 kmh^{-1}`

d) `40 kmh^{-1}`

Question 9: An object travels `20 m` in `5 s` and then author `40 m` in `5 s`. What is the average speed of the object?

a) `2 ms^{-1}`

b) `12 ms^{-1}`

c) `6 ms^{-1}`

d) `0 ms^{-1}`

Question 10: Area under the velocity–time graph gives ________.

a) displacement

b) distance

c) velocity

d) time

Question 11: The directions of both displacement and average velocity are ________.

a) The same direction

b) The opposite direction

c) (a) and (b)

d) none of above

Question 12: If a football kicked from the ground moves with a velocity of `20 ms^{-1}` making `30°` with the horizontal, find its vertical displacement and horizontal displacement after `1 sec`.

(Take `g`=`10 ms^{-1}`)

a) `5m, 20\sqrt{3}m`

b) `5m, 10\sqrt{3}m`

c) `10m, 10\sqrt{3}m`

d) `20\sqrt{3}m,5m`

Question 13: The variation of the velocity of a particle moving along a straight line is illustrated in the graph given below. The distance covered by the particle in `4 sec.` is _________ `m`.

a) `20`

b) `35`

c) `40`

d) `55`

Question 14:  A stone is dropped from the top of a tower and

allowed to travel freely under gravity. What is the initial velocity of the stone?

a) minimum

b) maximum

c) zero

d) Nun of these

Question 15: A bus travels the first one-third distance at a speed of `10 kmh^{-1}`, the next one-third distance at a speed of `20 kmh^{-1}`, and the next one-third distance at a speed of `30 kmh^{-1}`. The average speed of the bus is

a) `20 ms^{-1}`

b) `\frac{50}{11}ms^{-1}`

c) `\frac{180}{11}ms^{-1}`

d) `30 ms^{-1}`

Question 16: During an experiment, a signal from a spacecraft takes `5 min.` to reach the earth. What is the distance of space from the station on earth?

a) `9\times10^{7}km`

b) `9\times10^{-7}km`

c) `9\times10^{5}km`

d) `9\times10^{-5}km`

Question 17: A train that is `50 m` long, walking on a straight and flat track reaches a pole in `5 s`. Find the speed of the car.

a) `50 ms^{-1}`

b) `15 ms^{-1}`

c) `10 ms^{-1}`

d) none of above

Question 18:   A train which is `50 m` long, walking on a straight and flat track reach a pole in `5 s`. How much time will the train take to cross the `450 m` long bridge?

a) `45 s`

b) `50 s`

c) `25 s`

d) `10 s`

Question 19: A motor car travels a certain distance at a speed of `50 kmh^{-1}` and returns at a speed of `40 kmh^{-1}`. Calculate its average speed for the whole journey.

a) `44.44 kmh^{-1}`

b) `45.44 kmh^{-1}`

c) `40 kmh^{-1}`

d) `40.44 kmh^{-1}`

Answer key

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