Consult multiple-concept example 9 to explore a model for solving this problem. a person pushes on a 63-kg refrigerator with a horizontal force of -270 n; the minus sign indicates that the force points in the -x direction. the coefficient of static friction is 0.67. (a) if the refrigerator does not move, what are the magnitude and direction of the static frictional force that the floor exerts on the refrigerator? (b) what is the magnitude of the largest pushing force that can be applied to the refrigerator before it just begins to move? assume g = 9.8 m/s2.

 a ) 270 N

b )413.65 N

Explanation:

weight of the refrigerator = reaction force ( R )

= mg

= 63 x 9.8

R = 617.4 N

Maximum friction possible

= coefficient of friction x R

= .67 X 617.4

= 413.65 N

When force 270 N is applied , due to friction,  the body does not move .

The friction force adjusts itself to the external applied force to prevent the body to budge.

Hence the friction force acting in this situation = 270 N

b ) The maximum friction possible is 413.65 . If we apply a force equal to or exceeding 413.65 N , body will move. Hence 413.65 N is the answer.

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s

d. air pressure decreases as altitude increases.