Question

A 70-N block rests on a 30° inclined plane. a. determine the normal force. b. determine the friction force that keeps the block from sliding. c. what push directed up the plane will cause the block to move up the plane with constant speed if the force of friction is 18 N? draw a neat, labeled free body diagram.

Answer 1

Given that:

W = weight of the block = mg = 70 N

mass of the block is given as

m = W/g

m = 70/9.8 = 7.14 kg

a)

N = normal force on the block

Perpendicular to incline , force equation is given as

N = m g cos30

inserting the values

N = (70) Cos30

N = 60.6 N

b)

f = frictional force acting on the block to keep it from sliding

Parallel to incline force equation is given as

f = m g Sin30

f = (70) Sin30

f = 35 N

c)

F = pushing force

f = frictional force = 18 N

Parallel to incline force equation is given as

F = f + mg Sin30

F = 18 + (70) Sin30

F = 53 N