Gravity and Weight

By Selma Walsh on Jan 25, 2017

History:

People have been weighing objects forever, but it was the Greek people who first tried to figure out what weight is and how to explain weight.  A Greek man named Archimedes said weight was determined by (opposition of buoyancy) whether objects sink or float.  An Ancient Greek named Euclid was the first to say that “weight is the heaviness or lightness of one thing compared to another, as measured by a balance.” About 300 years ago, a scientist from England, Isaac Newton, determined that weight is the “force” of an object depending on the amount of stuff/matter the object is made of (mass) and the pull of gravity on the object.  Objects weigh less on the moon than they do on Earth because there is less gravity (W=mg).
 

Science Process Skills:

  • Identify properties of objects
  • Question, explore, observe, record and share information
  • Compare properties of one object to the properties of another object
  • Argue based on evidence
  • Use science tools to determine the weight of an object
 
 

Materials

  1. Paper folded in half and labeled (one half “heavy” and the other half “light”).
  2. Variety of objects with varying degrees of weight (block, rock, pebbles, feather, plastic toys, sponges, balls, etc.)
  3. Pan balance
  4. Units for weight, standard or nonstandard (grams, ounces, beans, pennies)
  5. Standard scales and spring scales
 

Procedure

Part I:  Compare and describe 2 objects as heavy or light

Explain and Demonstrate: 
  1. Given two objects, use your hands to compare and identify the heaviest object and the lightest object by placing the objects on designated area of a labeled, folded, piece of paper. 
  2. Compare the objects by placing one object in one pan of the balance and the second object in the other pan of the balance.
  3. Based on observation (evidence) of the position of the pan (up or down), identify the object as heavier or lighter.
    • Examples:
      • The pan with the rock is down.  The rock is heavier than the feather.  
      • The pan with the feather is up.  The feather is lighter than the rock.
  4. Weigh each object and record the weight on a class chart.

class chart of weights

Continue to Part II, or compare two new objects.  

Part II:  Compare the weight of 3 objects close in weight

  1. Students receive 3 objects to compare.
  2. Allow a minute or two for the students to manipulate the objects.
  3. Ask students to place the objects in order from the lightest to the heaviest.  May use a labeled piece of paper if needed.
  4. Students will weigh each object using the pan balance and place the objects in the correct order (lightest to heaviest).
  5. Record the weights on a class chart.
  6. As a class, compare the data and make conclusions for the correct order of the weights from lightest to heaviest. 
class chart of weights of different objects   Note:  this chart is only an example, any objects may be used.   The higher the skills of the student, the closer the weights of the objects.  

Part III:  Extensions to every day life

  • Show the students several tools used for weighing objects (measuring the force of gravity):  spring scale, bathroom scale, food scale etc.
  • Allow students to explore the scales with a selected object.
  • Show the students examples of weight on the labels of different cans of food
* Do not allow students to stand on the bathroom scale.     

NGSS Standards:

3-PS2-1 Motion and Stability: Forces and Interactions

Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object

Collage for gravity and weight
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