An angle of repose less than 25 degrees indicates good flowability.

• A. True
• B. False
• C. Not Sure
• D. Not Applicable

Answer: (A)

Angle of repose is a quick way to gauge how freely a powder flows by looking at the slope of a pile it forms when poured. When particles don’t stick together much and can slide past one another easily, the pile is relatively flat and the angle is small. Conversely, strong interparticle forces or moisture cause clumping and a steeper pile.

If the measured angle of repose is less than 25°, the slope is not steep, which means the powder flows readily. That’s why this indicates good flowability. In practice, powders with angles below about 25° are considered good or free-flowing, while larger angles point to progressively poorer flow, influenced by particle size, shape, moisture, and surface roughness.