A person is trying to judge whether a picture (mass = 2.34 kg) is properly positioned by temporarily pressing it against a wall. The pressing force is perpendicular to the wall. The coefficient of static friction between the picture and the wall is 0.710. What is the minimum amount of pressing force that must be used?
To prevent the picture from sliding down the wall, the static friction force must be equal to the weight of picture. Let F be the horizontal force.
Ff = 0.710 * F
Weight = 2.34 * 9.8 = 22.932 N
0.710 * F = 22.932
F = 22.932 ÷ 0710
This force is approximately 32.3 N
mg = μF
F = μ/mg
F = 0.710/(2.34*9.8)
F = 32.3 N
Minimum amount of pressing force that must be used is 32.3 N