Lab 3: Motion with Non- uniform Acceleration University of Michigan Physics Department Mechanics and Sound Intro Labs

In Lab 2, you explored the motion of objects whose acceleration was constant. In this Lab, you will consider the more interesting case in which an object’s acceleration changes. There are many kinds of motion that do not have constant acceleration. You might think of driving a car, in which you change your acceleration by applying pressure to the pedals. Today, you will study the motion of falling objects where the force of air resistance is amplified.  Galileo Galilei showed by experiment that objects of different masses fall at the same rate in the absence of air resistance. You will study motion that is affected by air resistance today.

To quickly review, forces are vector quantities, meaning they have both a magnitude and direction. Falling objects experience a downward force due to the Earth’s gravitational field, and in all but ideal cases, a resistive force called air resistance. It is important to note that this force, sometimes called drag, depends upon the speed of the object, that is, the object experiences a stronger force the faster it goes. For a full discussion of the air resistance force, see your lab manual.  position vs. time data for several objects experiencing different drag forces.

You have seen the equipment that you will use in this lab already. The sonic ranger is again placed under the vacuum release system which you will use to drop various objects. In this lab, you will first drop balloons and then drop cones of varying mass to study the effects of the air resistance force on mass and velocity. You will need to blow up a balloon to about eight inches in diameter, and you will use the same vacuum nozzle that you used to hold the balls in Lab 1 to hold the balloons.  A selection of objects that you will drop in this lab and their corresponding vacuum tube nozzles

You will need to switch nozzles in order to hold the various objects above the sensor. To switch nozzles, you press the metal tab above the nozzle and pull downward. Then you can insert the new nozzle into the system. Metal Tab  A close up of the vacuum- release system holding a cone. The metal tab is used to switch vacuum attachments.

After you have completed this lab, you will have explored motion in two basic cases. Motion with constant acceleration can be modeled easily by the kinematics equations, and motion with non-uniform acceleration requires a bit more clever approach. Lab 4 will deal with motion in two dimensions. A typical data plot for this experiment ^