a window washer pushes his scrub brush up a vertical window at a constant speed by applying a force f. the brush weighs 8N and the coefficient of friction is 0.4. calculate a) the magnitude of the force f. b) the normal force exerted by the window on the brush.
If v=const => a=0
f=F(fr)+mg
If f is directed vertically N=0 => F(fr)=μN=0
=> f=mg
no
To find the magnitude of the force applied by the window washer (f), we can use the following equation:
Net Force = Force Applied - Force of Friction
Since the window washer is pushing the scrub brush upward at a constant speed, the net force is zero. The force of friction can be calculated using the equation:
Force of Friction = Coefficient of Friction * Normal Force
Let's first calculate the force of friction:
Force of Friction = 0.4 * Normal Force
Now, we can equate the net force to zero:
0 N = f - 0.4 * Normal Force
Since the scrub brush is in equilibrium, its weight is balanced by the normal force exerted by the window. The normal force is equal to the weight of the brush, which is 8N. Therefore:
0 N = f - 0.4 * 8 N
To isolate the force applied by the window washer (f), we rearrange the equation:
f = 0.4 * 8 N
f = 3.2 N
a) The magnitude of the force applied by the window washer is 3.2 N.
b) The normal force exerted by the window on the brush is equal to the weight of the brush, which is 8N.