Laws of Motion

• Question 485

## Two fixed frictionless inclined planes making an angle 30° and 60° with the vertical are shown in the figure. Two blocks A and B are placed on the two planes. What is the relative vertical acceleration of A with respect to B? 4.9 ms-2 in horizontal direction 9.8 ms-2 in vertical direction zero 4.9 ms-2 in vertical direction

Solution

D.

4.9 ms-2 in vertical direction

For the motion of block along inclined plane
mg sin θ =ma
a = g sin θ
where a is along the inclined plane.
The vertical component of acceleration is g sin2θ
Therefore, the relative vertical acceleration of  A with respect to B is
g (sin260 - sin230) = g/2 = 4.9 ms-2 (in vertical direction)

Question 486

Solution

C.

Question 487

## A particle A of mass m and initial velocity v collides with a particle B of mass m/2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths λA to λB after the collision is

Solution

D.

By conservation of linear momentum
Question 488

## A body of mass m = 3.513 kg is moving along the x-axis with a speed of 5.00 ms−1.The magnitude of its momentum is recorded as 17.6 kg ms−1  17.565 kg ms−1 17.56 kg ms−1 17.57 kg ms−1

Solution

A.

17.6 kg ms−1

P = mv = 3.513 × 5.00 ≈ 17.6