Paragraph: A small block of mass $1 \mathrm{~kg}$ is released from rest at the top of a rough track. The…

Paragraph: A small block of mass $1 \mathrm{~kg}$ is released from rest at the top of a rough track. The track is a circular arc of radius $40 \mathrm{~m}$. The block slides along the track without toppling and a frictional force acts on it in the direction opposite to the instantaneous velocity. The work done in overcoming the friction up to the point $Q$, as shown in the figure below, is $150 \mathrm{~J}$. (Take the acceleration due to gravity, $g=10 \mathrm{~m} \mathrm{~s}^{-2}$ ).

Question: The speed of the block when it reaches the point $Q$ is
  1. 5 ms - 1
  2. 10 ms - 1
  3. 10 3 ms -1
  4. 20 ms - 1

Solution

Apply conservation of energy,
PE-Wf=KE
MgRsin30°-150=12Mv2
MgR2-150=12Mv21×10×20-150=12×1×v2v=10 m s-1
  .

Asked in: JEE Advanced 2013 (Paper 2)

Practice more Work Power Energy questions on Aicharya