5.35 A block of mass 15 kg is placed on a long trolley. The coefficient of static friction between the block and the trolley is 0.18. The trolley accelerates from rest with 0.5 m s^-2 for 20 s and then moves with uniform velocity.

Discuss the motion of the block as viewed by

(a) A stationary observer on the ground

(b) An observer moving with the trolley

<p>Mass of the block = 15 kg</p><p>Coefficient of static friction between the block and the trolley &nbsp;<span title="Click to copy mathml"><math><mi>μ</mi></math></span>&nbsp;= 0.18</p><p>Acceleration of the trolley = 0.5 m/s2</p><p><strong> (a)</strong> Force experienced by block, F = MA = 15 <span title="Click to copy mathml"><math><mo>×</mo></math></span>&nbsp;0.5 = 7.5 N. This fore acts in the direction of motion of the trolley</p><p>Force of friction, Ff =&nbsp;<span title="Click to copy mathml"><math><mi>μ</mi><mi>m</mi><mi>g</mi></math></span>&nbsp;= 0.18&nbsp;<span title="Click to copy mathml"><math><mo>×</mo><mn>15</mn><mi></mi><mo>×</mo><mn>10</mn></math></span>&nbsp;N = 27 N</p><p>Force experienced by the block is less than the friction, hence for a stationary observer on the ground, the block will be stationary</p><p><strong> (b)</strong> When an observer moves with the trolley, the trolley will appear to be at rest</p>

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