A 10 kg block is initially at rest on the floor. Then a force of 30 N pushes hor

Question

A 10 kg block is initially at rest on the floor. Then a force of 30 N pushes horizontally the block. If the coefficient of static friction between the block and the floor is p8 = 0.33 and the coefficient of kinetic friction between the block and the floor is pK = 0.20, what is the acceleration of the block in m/s2? 0.23 0.0 1.0 -1.0 An 89 kg man runs up a flight of stairs as shown in the figure. Hew much power is expended by the man to get to the top of the stairs in 5 seconds? 3490 W 4360 W 2620 W 524 W

Explanation / Answer

11.

normal reaction = 10*9.8 N

=> static friction force = (10*9.8)*(0.33 = 32.34 N

since, force applieed is less than static friction force => the block won't move

Hence, its acceleration = 0

correct answer is b)

12.

change in his potential energy = mgh = 89*9.8*3 = 2616.6 J

=> Power = 2616.6/5 = 523.32 W = 524 W

correct answer is d)

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