Machine Design
In replacing the V-belts, a complete set of new belts is used instead of replacing a single damaged belt because

New and old belts will cause vibrations
Only one belt cannot be fitted with other used belts
The new belt will carry more than its share and result in short life
Belts are available in sets

ANSWER DOWNLOAD EXAMIANS APP

Machine Design
In a band and block brake, the ratio of tensions on the tight and slack sides of band is given by (where μ = Coefficient of friction between the blocks and the drum, θ = Semi-angle of each block subtending at the centre of drum, and n = Number of blocks)

T₁/T₂ = [(1 - μ tanθ)/ (1 + μ tanθ)]n
T₁/T₂ = [(1 + μ tanθ)/ (1 - μ tanθ)]n
T₁/T₂ = μθ × n
T₁/T₂ = (μθ)n

ANSWER DOWNLOAD EXAMIANS APP