# KVPY Stream-SA (Class 11) Physics: Questions 198 - 202 of 252

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## Question number: 198

MCQ▾

### Question

Two starts each of 1 solar mass are approaching each other for a head-on collision. When they are at a distance of 3 ⨯ 107 km, their speeds are negligible. The speed with which they collide is –

(The radius of each star is 105 km, assume the stars to remain undistorted until they collide. . )

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 199

MCQ▾

### Question

The activity of a radioactive sample reduces to of its original value in 2 hours. What will be its activity in 6 hours?

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 200

MCQ▾

### Question

The energy required to accelerate a car from rest to 12 ms-1 is E. What energy will be required to accelerate the car from 12 ms-1 to 24 ms-1?

### Choices

Choice (4) Response

a.

E

b.

7E

c.

5E

d.

3E

## Question number: 201

MCQ▾

### Question

A train of length l (180 m) is going towards north directional constant speed v1=16 m/s. A parrot flies at a constant speed of v2 = 4 m/s towards south parallel to be railway track. The time taken by the parrot to cross the train is –

### Choices

Choice (4) Response

a.

7 s

b.

3 s

c.

9 s

d.

5 s

## Question number: 202

MCQ▾

### Question

The isotopes 238U and 235U occur in nature in the ratio 150: 1. Assuming that at the time of earth formation they were present in equal amount; make an estimation of the age of the earth. The half-lives of 238U and 235U are and respectively.

### Choices

Choice (4) Response

a.

b.

c.

d.

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