Q.

A block of base 10 cm×10 cm and height 15 cm is kept on an inclined plane. The coefficient of friction between them is 3. The inclination θ of this inclined plane from the horizontal plane is gradually increased from 0°. Then                        [2009]

1 at θ=30°, the block will start sliding down the plane  
2 the block will remain at rest on the plane up to certain θ and then it will topple  
3 at θ=60°, the block will start sliding down the plane and continue to do so at higher angles  
4 at θ=60°, the block will start sliding down the plane and on further increasing θ, it will topple at certain θ  

Ans.

(2)

Maximum angle not to slide the block, angle of inclination = angle of repose,

i.e., tan-1μ=tan-13=60°

For the block to topple, the condition of the block has been shown in the figure.

In POMtanθ=PMOM=10/215/2=5 cm7.5 cm=23

So, θ<60°.

From this we can conclude that the block will topple at a lesser angle of inclination. Clearly the block will remain at rest on the plane up to a certain angle θ and then it will topple.