Question

A block of mass 3.0 𝑘𝑔 slides with uniform velocity down a plane inclined 25o with the horizontal. If the angle of inclination is increased to 40o , what will be the acceleration of the block? 

Answer 1

$mg\sin25°-\mu mg\cos25°=0\to \mu =\tan25°$

$mg\sin40°-\mu mg\cos40°=ma\to a=g(\sin40°-\tan25°\cos40°)=$

$=9.8\cdot(\sin40°-\tan25°\cos40°)=2.8\ (m/s^2)$