# NEET (NTA)-National Eligibility cum Entrance Test (Medical) Physics: Questions 428 - 430 of 2320

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## Question number: 428

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MCQ▾

### Question

particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration ac is varying with time t as ac = k 2 rt 2, where k is a constant. The power delivered to the particle by the force acting on it will be

### Choices

Choice (4)Response

a.

mk 2 t 2 r 2

b.

m 2 k 2 t 2 r 2

c.

mk 2 r 2 t

d.

mk 2 t 2 r

## Question number: 429

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MCQ▾

### Question

The charges on two spheres are + 7 μ C and -5 μ C respectively. They experience a force F. If each of them is given an additional charge of -2 μ C, the new force of attraction will be

### Choices

Choice (4)Response

a.

F

b.

c.

d.

2F

## Question number: 430

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Assertion-Reason▾

### Assertion (Ꭺ)

A river is flowing from east to west at a speed of 5m/min. A man on south bank of river, capable of swimming 10 m/min in still water, wants to swim across the river in shortest time. He should swim due north.

### Reason (Ꭱ)

For the shortest time the man needs to swim perpendicular to the bank.

### Choices

Choice (4)Response

a.

Both Ꭺ and Ꭱ are false

b.

Both Ꭺ and Ꭱ are true but Ꭱ is NOT the correct explanation of Ꭺ

c.

Both Ꭺ and Ꭱ are true and Ꭱ is the correct explanation of Ꭺ

d.

Ꭺ is false but Ꭱ is true

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