Question

A block of mass 2.5 kg is kept on a rough horizontal surface. It is found that the block does not slide if
a horizontal force less than 15N applied to it. Also it is found that it takes 5 second to slide through the
first 10 m if a horizontal force of 15N is applied and the block is gently pushed to start the motion. The
values of coefficient of static and kinetic friction between the block and the surface are (g = 10 ms-2)
a) 0.60, 0.52
b) 0.15, 0.52
c) 0.25, 0.60
d) 0.60, 0.15 ​

Answer 1

Answer:

hope this will help you.

Answer 2

ANSWER:

Coefficient of kinetic friction = 13/25 = 0.52 ANS

Coefficient of static friction = 15/25 = 0.60 ANS

EXPLANATION:

The weight of the mass of block, m = 2.5 kg

Now comparing the values of the weight of block = size of Normal force = mg = (2.5)(10) = 25 N

The horizontal force applied = 15 N (capable to move blocks)

$\mathrm{d}=1 / 2 \mathrm{at}^{2}${where d = 10 m, and t = 5 s, and "a" = block's acceleration}

$\mathrm{a}=2 \mathrm{d} / \mathrm{t}^{2}=20 / 25=0.8 \mathrm{m} / \mathrm{s}^{2}$

The net force acting on the block of weight = ma = (2.5)(0.8) = 2.0 N

The force required to oppose the external force = 15 - 2 = 13 N

The value of the Kinetic Friction Force = 13 N

Therefore, dividing the Kinetic Force Friction and Horizontal Force by Normal Force we get

Coefficient of kinetic friction = 13/25 = 0.52 ANS

Coefficient of static friction = 15/25 = 0.60 ANS