Force Fiesta!

Goals:

  • Get familiar with the various

forces in practical situations

  • Be able to estimate the strength of a particular force (within a very wide range)
  • Record data neatly and clearly in a well-organized data table.
  • Answer questions clearly, with part of the question in your response so the reader doesn’t have to refer back to the question to know what you’re answering.

Protocol:

  • You will travel with your group to each of the five stations to investigate specific forces. At each station, have one of your group members perform the specified activity, and answer the associated questions.
  • Create one big table using the example below as a guide to record and label all your data. Include units with your forces! There will be 12 rows in your table (after the top row with the column titles). All forces should be in the unit of Newtons.
  • Answer the numbered questions after the table.
  • All data and answers should be on separate paper, not on the lab itself.

Station/Activity / Description / Trial 1 / Trial 2 / Trial 3 / Notes/comments
St 1, Act 1 / Hung a mass
St 1, Act 2 / Person pulled string

Station #1: Terrific Tension

At this station you will investigate and measure tension forces. You will find spring scales, strings, and weights

  • Activity 1: Tie one end of a string to amass, and the other end to the spring scale. Hold up the scale and allow the weight to hang freely from it. Record the reading on the scale. In the comments column, write what the mass has printed on it.
  • Activity 2: Remove the weight from the string and instead have one person hold the scale while another pulls on the string. Don’t max out the scale, but get a feeling for how much tension there is in the string. Record the reading on the scale.

Station #2: Fabulous Friction

At this station you will find some blocks, a piece of sand paper, some strings, some weights, and spring scales.

  • Activity 1: Attach the spring scale to the block, and pull it horizontally across the table. Try 2-3 trials and record each.
  • Activity 2: With the same apparatus, place a weight on top of the block and pull it horizontally across the table. Record 2-3 trials.
  • Activity 3: With the same setup as Activity 1, drag the block across the sandpaper. Record 2-3 trials.
  • Activity 4: With the same setup as Activity 2, drag the block across the sandpaper. Record 2-3 trials.

Station #3: Dubious Drag

At this station, you will experience some typical drag forces by pulling a piece of plastic through water, and by using a parachute.

  • Activity 1 – water jug: holding the spring scale, suspend the “drag device” at rest and get a reading of the force needed to hold it still.
  • Activity 2 – water jug: holding the spring scale, pull up on the string to lift the drag device up through the water inside the water jug. Do this a few times to get a feel for it, and then record your last 2-3 pulls.
  • Activity 3 – parachute: holding a spring scale with the parachute attached to the hook, walk briskly down the hall pulling the parachute behind you. Or hold your arm out in front of you and spin around (safely) so the parachute fills up and you get a reading on the scale. Try this 2-3 times. Record the force each time.

Station #4: Neato Normal

In this station you will find a force plate attached to a computer.

  • Activity 1 – standing still: stand still on the force plate and record the force.
  • Activity 2 – jumping! Jump up and down gently (don’t slam your feet, the force plate’s internals can be broken), and record the highest and lowest values you read on the graph.
  • Activity 3 – leaning: have a person in your group hold the bathroom scale, up against the wall. Have a second person lean against the scale so it is between their hand and the wall. Note: 1 lb = 4.45 Newtons. Record the force in Newtons. Be careful not to drop the scale!

Station #5: Super Spring

In this station, you will create a graph from data you obtain while pulling a spring.

  • Activity 1:
  • Connect a spring to the scale and let them lay flat on the table.
  • Pin one end of the spring down with a finger, so that the other end can be pulled by the scale (when you measure, pull on the scale, not the spring).

  1. With no pull on the spring, place a ruler so that 0cm lines up where the scale connects to the spring (as shown below). This way, you will measure how much the spring stretches (yes), rather than the total length of the spring (no).

YESNO

  1. Stretch the spring 1cm, 2cm, 3cm… continue up to 10cm, recording the force for each location.

Questions:

Station 1:

  1. For each activity, what object is exerting a tension force on the scale?
  2. In your own words, describe or define tension.

Station 2:

  1. As you dragged the blocks across the surface, were you observing kinetic or static friction? Support your answer.
  2. What are some factors which affect how much friction there was? (State the factor, and also specify whether it caused more or less friction).
  3. In your own words, describe or define friction.

Station 3:

  1. In your own words, describe or define drag.

Station 4:

  1. What was the situation when the force plate had the lowest reading?
  2. What was the situation when the force plate had the highest reading?
  3. In your own words, describe or define Normal force.

Station 5:

  1. Record your data in a table (separate from the big one for Stations 1-4) using the example below.
  2. Create a graph of that data, with Force on the Y-axis and Stretch on the X-axis.

Stretch / Force
1cm
2cm
Etc.
  1. Describe the relationship (as specifically as you can) between Force and Stretch. (Is there a pattern? What is it?)
  2. In your own words, describe or define the spring (aka elastic) force.