Physics(Exams > Bitsat ) Questions and answers for exam Preparation

Exams > Bitsat

PHYSICS MCQs

Total Questions : 421 | Page 11 of 43 pages

A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle . The motion of the particle takes place in a plane . It follows that

its velociy is constant
its kinetic energy is constant
it moves in a circular path
both (B) and (C) are correct

Discuss Question

Answer: Option D. -> both (B) and (C) are correct

A force of constant magnitude which is always perpendicular to the velocity of the particle does not do work . Hence , K.E. of the particle is constant . As force is perpendicular to the velocity the particle moves in a circular path

Question 102.

A parrot is sitting on the floor of a closed glass cage which is in a boy 's hand . If the parrot starts flying with a constant speed the boy will feel the weight of cage as

unchanged
reduced
increased
nothing can be said

Discuss Question

Answer: Option A. -> unchanged

Since cage is closed , external force on the system remains constant . Hence , the boy will feel the weight of cage as unchanged.

Question 103.

In the superhit film 'Raja Hindustani' Amir Khan greets his beloved by shaking hand .What kind of force do they exert ?

nuclear
gravitational
weak
electromagnetic

Discuss Question

Answer: Option D. -> electromagnetic

Question 104.

Two bodies have same mass and speed , then

their momentums are same
the ratio of momenums is not determined
the ratio of their magnitudes of momentum is one
both (B) and (C) are correct

Discuss Question

Answer: Option D. -> both (B) and (C) are correct

Question 105.

Impulse indicates

the momentum generated in the direction of force
the combined effect of mass and velocity
the main characteristics of particle nature
both (B) and (C) are correct

Discuss Question

Answer: Option D. -> both (B) and (C) are correct

Question 106.

Rain drops fall vertically at a speed of 20 m/s . At what angle do they fall on the wind screen of a car moving with a velocity of 15 m/s if the wind screen velocity inclined at an angle of `23^circ` to the vertical ?`(cot^-1 4/3 = 37^circ)`

`60^circ`
`30^circ`
`45^circ`
`90^circ`

Discuss Question

Answer: Option A. -> `60^circ`

`tan (90^circ - theta) = 20/15`

`:.` ` cot theta = 20/15` = `4/3`

`rArr theta = 37^circ`

`:.` `alpha = 37^circ + 23^circ` = `60^circ`

Question 107.

A motor boat covers the distance between two spots on the river banks in `t_1 = 8 h` and `t_2 = 12 h` in down steam and upstream respectively . The time required for the boat to cover this distance in still water will be

6.9 hr
9.6 hr
69 second
96 second

Discuss Question

Answer: Option B. -> 9.6 hr

Let the distance between spots A and B is `l`.

`u`= speed of river stream

`v` = speed of motor boat in still water

During downstream ,

`t_1 = (l)/(v + u)`.........................................................(i)

Similarly in upstream

`t_2 = (l)/(v - u)`.....................................................(ii)

In still water , `t = l/v` .........................................................(iii)

After solving equation (i), (ii) and (iii) , we get .

`t `= 9.6 hour.

Question 108.

A beautiful girl going eastwards with a velocity of 4 km/hr, find that the wind appears to blow directly from the north . She doubles her speed and the wind seems to come from north east . The actual velocity of wind is .

`4sqrt(2)` km/hr owards south east
`4sqrt(2)`km/hr towards north west
`2sqrt(2) `km/hr towards south east
None of the above.

Discuss Question

Answer: Option A. -> `4sqrt(2)` km/hr owards south east

Question 109.

A man rows directly across a river in time t second and rows an equal distance down the stream in T second . Find the ratio of man's speed in still water to the speed of river water.