Question

A 60-lb block rests on a smooth
horizontal surface. Find the horizontal
force need just to start motion if its =
0.5.

Answer 1

Answer:30

Explanation:

So, we need to fnd the horizantal force need to start motion if it is=0.5

60/0.5

=60*5/10

=300/10

=30

So, this the final answer

Answer 2

Given:

A 60-lb block rests on a smooth horizontal surface.

To find:

The horizontal force need just to start motion if its $\mu$ = 0.5.

Calculation:

First of all, we need to convert the mass from lb unit to kg unit :

$\boxed{60 \: lb = 60 \times 0.454 = 27.21 \: kg}$

Now, at critical conditions , the applied force have to be slightly greater than max static friction in order to move the block :

$\therefore \: F_{applied} = f_{static}$

$\implies\: F_{applied} = \mu_{s} \times (normal \: reaction)$

$\implies\: F_{applied} = \mu_{s} \times (mg)$

$\implies\: F_{applied} =0.5\times (27.21 \times 10)$

$\implies\: F_{applied} =136.05 \: N$

So, the applied force have to be slightly greater than 136.05 N.