Question

1. A mass of 9.9 kg is resting on a horizontal surface without friction. A force is applied vertically upward to the mass. What does the amount of this force need to be in order to begin to pull the mass off the surface, in Newtons?

2. A mass of 8 kg is resting on a horizontal surface without friction. A force of 143 Newtons is applied in the +x direction, a force of 19 Newtons is applied in the -x direction, and a force of 11 Newtons is applied in the -y direction (downward). What is the acceleration of the mass in m/s2? If in the -x direction, include a negative sign.

Answer 1

1.

Given mass m=9.9kg

Force F required to pull the object vertically upwards

F=mg = 9.9 *9.81

= 97.119 N

ANSWER : F = 97.119 N

2.

Given Mass = 8kg

Force = mass * acceleration

First ,Find vertical and horizontal forces acting on body

Fx = 143 -19 = 124 N (force 19N is in -x direction)

Fy = -11-mg = -11 -8*9.81 = -89.48 N

Since there is no friction between object and surface ,no need of Fy

Fx = m*a

accleration = Fx/m = 124/8 = 15.5 m/s² (+ve x direction )

ANSWER : a= 15.5m/s²