Search our library of A Level questions

Top answers

All subjects

A Level

Why is the refractive index of water bigger than that of air?

The refractive index is related to the perceived speed at which light is going in that medium. Water is more dense than air, ie there are more particles occupying a given space. So when light travels thro...

Answered by Miyabi B. • Physics tutor

9202 Views

"An inclined plane at an angle of 25 degrees to the horizontal has a pulley at its top. A 30kg block on the plane is connected to a freely hanging 20kg block by means of a cord passing over the pulley. From rest how far will the 20kg block fall in 2s?

For the 20kg block choose downward as positive and for the 30kg block choose the x axis along the incline as positive.Apply Newton's second law of motion to each block separately.The pulley is frictionles...

Answered by Joni W. • Physics tutor

4619 Views

Express cos(2x) in terms of acos^2(x) + b

cos(2x)=cos²(x) - sin²(x)use sin²(x) = 1 - cos²(x)so cos(2x)=cos²(x) - (1 - cos²(x))cos(2x)=2cos²(x) - 1so a = 2 and b = -1

Answered by • Maths tutor

3193 Views

Given that f(x) = x^2 (3x - 1)^(1/2) find f'(x)

This is an example of a question using the product rulelet u = x² and v = (3x - 1)^1/2then u' = 2x and v' = 3 X 1/2 (3x - 1)^-1/2 using the product rule we get f'(x) = x

Answered by • Maths tutor

3650 Views

By comparing the forces involved, explain why hydrogen iodide (HI) would have a higher boiling point than hydrogen bromide (HBr)?

stronger van der waal bonds because iodide ion (I-) has a larger electron cloud so more polarisable so istantaneouos dipoles happen more often and more strongly, so more energy is needed to overcome these...

Answered by Maddie W. • Chemistry tutor

7219 Views