Question

A uniform disc of mass $0.5\, kg$ and radius $r$ is projected with velocity $18 \,m / s$ at $t=0$ s on a rough horizontal surface It starts off with a purely sliding motion at $t=0\, s$ After $2\, s$ it acquires a purely rolling motion (see figure) The total kinetic energy of the disc after $2 \,s$ will be ______ $J$ (given, coefficient of friction is $0.3$ and g=10m/s2)

Answer 1

The correct answer is 54.
a=−μk​g=−3
V=18−3×2
V=12m/s
KE=21​mv2+21​2mr2​r2v2​
KE=43​mv2
KE=3×18=54J