Lessons 3: 1D Dynamics (Invisible Forces)

Six Homework Problems for Lesson 03

Write your solutions to the following problems and submit them before 6 am on Monday, FEB. 3RD.

Submit to the SUBMIT folder on Priscilla or as an attachment to an e-mail message to rfuller@unlinfo.unl.edu or using this Web form.

Your Name:

  1. The coefficient of dynamic friction of a block on an inclined plane may be determined by raising the plane just enough so the block slides with uniform speed, and measuring the angle of inclination of the plane:

    1. Make a free-body diagram for the block.

    2. Derive a relationship between the angle and the coefficient of friction for these conditions.

  2. A block slides down an inclined plane of angle with constant velocity. It is then projected up the same plane with an initial speed v0.

    1. How far up the incline will it move before coming to rest?

    2. Will it slide down again? (Explain)

  3. A 29.0-kg block is pushed up a 37° inclined plane by a horizontal force of 440 N. The coefficient of friction is 0.250.

    Show your work and find:

    1. the acceleration;

    2. the velocity of the block after it has moved a distance of 6.0 m along the plane, assuming it started at rest; and

    3. the normal force exerted by the plane.

  4. A hockey puck having a mass of 0.110 kg slides on the ice for 15.2 m before it stops.

    1. Draw a free-body diagram of the puck, including the frictional force.

    2. If its initial speed was 6.1 m/s, what is the force of friction between the puck and ice?

    3. What is the coefficient of kinetic friction?

  5. A man pushes a board of mass m through a circular saw by pushing down on it with a stick as shown in the diagram.

    Find the force F that must be exerted to make the board slide with constant speed, in terms of the angle , the coefficient of friction, and the mass of the board.

  6. A 50-kg block on a plane inclined at 37° is acted upon by a horizontal force of 50 N. The coefficient of friction between block and plane is 0.300.

    1. Draw a free-body diagram of the block, assuming it is moving up the plane.

    2. What is the acceleration of the block if it is moving up the plane?

    3. How far up the plane will the block go if it has an initial upward speed of 4.0 m/s?

    7. Be sure to include your name on your submitted document.

    Be sure to hit the above Submit Query button if you're using the Web to submit!