A woman pushes a trunk on a railway platform which has a rough surface. She supplies a force of 100 N over a distance of 10 m. Thereafter, she gets progressively tired and her applied force reduces linearly with distance to 50 N. The total distance by which the trunk has been moved is 20 m.

If frictional force between trunk and rough surface is 50 N, then calculate the net work done by the two forces over 20 m.

1. 1000 J
2. 500 J
3. 750 J
4. 1500 J

Which of the following cannot be a decay product from the parent nuclei?

1. An isotope of parent nuclei
2. An isobar of parent nuclei
3. More stable daughter nuclei
4. None of the above

Assertion : The refractive index of a medium decreases with increase in wavelength of incident light.

Reason : The refractive index of a medium decreases with increase in temperature of medium.

1. Both Assertion and Reason are true.
2. Both Assertion and Reason are false.
3. Assertion is false but Reason is true.
4. Assertion is true but Reason is false.

The wave velocity, frequency and wavelength are related as

1. v = fλ

2. λ = vf

3. f = $\dfrac{λ}{v}$

4. v = $\dfrac{λ}{f}$