Question

What minimum amount of force is required to move a 10kg block kept on a horizontal surface. Given (${\mu }_s$=0.5), (${\mu }_k$=0.4) If the block was already moving then what would be the minimum force required to maintain its velocity at a constant value?

• A. 0N, 40N
• B. 50N, 0N
• C. 50N, 40N
• D. 40N, 50N

Answer 1

The correct option is C

50N, 40N

When static,

$f_{max}$ = ${\mu }_s$ x N

= 0.5 $\times$ mg

= 0.5 $\times$ 10 $\times$ 10

= 50N

$\therefore$ Minimum value of external force required to move it is 50 N

When moving

F = ${\mu }_k$ $\times$ N

= 0.4 $\times$ 10 $\times$ 10

= 40N

$\therefore$ When moving, minimum force required prevent it from accelerating/decelerating is 40N.