Find the change in temperature at which the velocity of sounds is 2/3 of velocity at STP.

Question 15
Step 1: Calculate the weight of the block.
$W = mg$
$m = 10~kg,\ g = 10~\mathrm{m/s^2}$
$W = 10 \times 10 = 100~\mathrm{N}$

Step 2: Component of weight parallel to the plane (produces motion down the plane).
$W_\parallel = W \sin \theta$