Two inclined frictionless tracks, one gradual and the other steep meet at A from where two stones are allowed to slide down from rest, one on each track (Fig. 6.16). Will the stones reach the bottom at the same time? Will they reach there with the same speed? Explain. Given θ1 = 30°, θ2 = 60°, and h = 10 m, what are the speeds and times taken by the two stones? | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-6 Work, Energy And Power

Q.25:- Two inclined frictionless tracks, one gradual and the other steep meet at A from where two stones are allowed to slide down from rest, one on each track (Fig. 6.16). Will the stones reach the bottom at the same time? Will they reach there with the same speed? Explain. Given θ1 = 30°, θ2 = 60°, and h = 10 m, what are the speeds and times taken by the two stones?

The given situation can be shown as in the following figure:

AB and AC are two smooth planes inclined to the horizontal at ∠θ1 and ∠θ2 respectively. As height of both the planes is the same, therefore, noth the stones will reach the bottom with same speed.
As P.E. at O = K.E. at A = K.E. at B
mgh = 1/2 mv12 = 1/2 mv22
v1 = v2
As it is clear from fig. above, accleration of the two blocks are a1 = g sin θ1 and a2 = g sin θ2
As θ2 > θ1
a2 > a1
From v = u + at = 0 + at
or, t = v/a
As t ∝ 1/a, and a2 > a1
t2 < t1
i.e., Second stone will take lesser time and reach the bottom earlier than the first stone.