Question

You pull with a force of 295 N on a rope that is attached to a block of mass 22 kg, and the block slides across the floor at a constant speed of 1.6 m/s. The rope makes an angle of 35 degrees with the horizontal. What is the net force on the block

Answer 1

Answer:

Fnet = 0

Explanation:

• Since the block slides across the floor at constant speed, this means that it's not accelerated.
• According Newton's 2nd Law, if the acceleration is zero, the net force on the sliding mass must be zero.
• This means that there must be a friction force opposing to the horizontal component of the applied force, equal in magnitude to it:

       $F_{appx} = F_{app} * cos \theta = 295 N * cos 35 = 242 N (1)$

• In the vertical direction, the block is not accelerated either, so the sum of the normal force and the vertical component of the applied force, must be equal in magnitude to the force of gravity on the block:

      $F_{appy} = F_{app} * cos \theta = 295 N * sin 35 = 169 N (2)$

⇒    169 N + Fn = Fg = 216 N  (3)

• This means that there must be a normal force equal to the difference between Fappy and Fg, as follows:
• Fn = 216 N - 169 N = 47  N (4)