Investigation Sequence

Gravity, acceleration, inertia, and friction

Written by: Ginger Hingst and Rick Steffenhagen Date

Focus Questions

Concepts

Content: Earth, Physical, & Life

Gravity, acceleration, inertia, and friction

Cross cutting concepts

Movement is an objects change in place or position.

Science Practice

Inquiry concepts

Personal, Social, Technology, Nature of Science, History

 

Background information

Movement is effected by many factors including gravity, acceleration, inertia and surface friction. Acceleration is the change in speed of an object. Inertia is the tendency of objects to stay in motion or to stay still. In order to start something moving or to stop it from moving, a force must be applied to overcome the inertia. A force can be a push, pull or throw. Gravity is a force that applies the same force on objects no mater what the weight of the object is. Surface friction can slow an object's acceleration and momentum (inertia). Variables that effect it include texture, weight, and shape.

Activity Sequence

  1. What is Inertia?
  2. Do heavy objects fall faster than light objects?
  3. How does gravity effect acceleration?
  4. Paper Airplanes.
  5. Ball on carpet/linoleum.
  6. Objects on ramp.
  7. Box and rubber band.

Activity Descriptions

Activity 1

Focus question: What is Inertia?

Materials: Water glasses, cards (4x4), and coins.

Procedure:

  1. Ask students what would happen if they are riding in a car and their mom applies the breaks (they feel like they are being pushed forward). Tell students that they are going to do a similar activity.
  2. Have students place card on glass, place coin in the middle of card.
  3. Ask the students what forces are acting on the penny.
  4. Ask students what would happen if the cardboard were suddenly taken away.
  5. Have the students give the card a quick flip so that the penny falls to the bottom of the cup.
  6. Ask how inertia had an effect on the penny, what force does the bottom of the glass have on the penny.
  7. Ask what would happen to the penny if no other force than gravity were applied to the penny.
  8. Ask student if they know what inertia is, if not define it as the tendency of objects to stay in motion or to stay still.
  9. Ask students where else they might see inertia in action (riding a bike).

Activity 2

Focus question: Do heavy objects fall faster than light objects?

Materials: Paper, balls of various sizes and weights.

Procedure:

  1. Ball up a piece of paper.
  2. Hold the ball of paper in one hand and a ball in the other.
  3. Predict which object will fall faster.
  4. Drop both objects at the same time (both objects should land at the same time).
  5. Repeat experiment with a variety of objects.
  6. For the last drop use a balled up piece of paper and a sheet of paper (the ball of paper should land first).
  7. Ask what could have caused the un-balled piece of paper to take longer to fall.
  8. What objects do people use to slow the effects of gravity (parachute), and how does it work?
  9. View video of feather and hammer dropping on the moon. (:47)

Activity 3

Focus question:How does gravity effect acceleration?

Materials: Ramp, ball or marble, tape measure, and clock.

Procedure:

  1. Make a ramp long enough for a sphere to roll down it for three or more seconds.
  2. Start the sphere at the top and mark where the sphere is at the end of 1 second, 2 seconds, and 3 seconds.
  3. Measure the distances and graph the results.
  4. Discuss what the results explain about acceleration and gravity.

Activity 4

Focus question: How does mass, acceleration, and inertia effect paper airplanes?

Materials: Several types of paper, and tape measure.

Procedure:

  1. Ask students how they would make a paper airplane so that it will fly furthest.
  2. Have students make as many paper airplanes as they can using a variety of kinds of papers, and designs so they can test a number of variables,
  3. Have the students stand on a line and throw the planes.
  4. Measure the distance the planes flew.
  5. Have the students measure their planes weight, and wing surface area.
  6. Have the class compare their plane’s features with the distance the planes flew.
  7. Add a paperclip to the plane.
  8. Test the plane to see how far it will fly this time.
  9. Keep adding weight to the plane and see how far it will fly.
  10. Ask how much weight is too much weight to add to the airplane.
  11. Discuss how real planes are designed with this information in mind.

Activity 5

Focus question: What is the differance or a ball rolling on a carpet or linoleum?

Materials: Marbles, tape measure, carpet, and linoleum floor.

Procedure:

  1. Have students predict if an object will slide farther on a rough or smooth surface.
  2. Place marble on the carpet floor.
  3. Flick the marble.
  4. Measure how far the marble rolled.
  5. Repeat procedure on the linoleum floor; remember to flick with the same force.
  6. Ask what may have caused the marble to role farther on the linoleum floor.
  7. Explain how this effect is friction.
  8. Ask where else the class may have experienced friction (pulling a wagon on gravel).

Activity 6

Focus question: How do objects roll on a ramp?

Materials: Tape, square of cardboard, toy car, eraser, coin, button, stone, and ruler.

Procedure:

  1. Tape one end of the cardboard to a desk.
  2. Pick one of the objects, feel the surface of the object and the ramp, and predict how high the free end of the cardboard will need to be lifted so the object selected can slide down the board.
  3. Place the object on the free side of the cardboard.
  4. Hold the ruler perpendicular to the desk.
  5. Lift the cardboard till the object starts to slide down the cardboard.
  6. Record the height the cardboard had to be lifted.
  7. Repeat experiment with all objects.
  8. Ask why the cardboard had to be lifted higher for some of the objects (some objects had more surface friction).

Activity 7

Focus question: What is friction and how strong is it?

Materials: Two pieces of string, rubber band, small cardboard box, tape, ruler, objects of different mass, smooth surface (desktop), and rough surface (carpet floor).

Procedure:

  1. Tie one end of a piece of string to the rubber band. Tie another piece of string on the other end of the rubber band. Tape one of the pieces of string to the side of the box securely.
  2. Have students predict how long the rubber band will have to stretch before the box begins to move.
  3. Place box on smooth surface.
  4. Pull the unattached end of the other string; use the ruler to measure the length of the stretched rubber band just as the object begins to move.
  5. Record the length of the stretched rubber band.
  6. Place some objects in the box and repeat steps 3 &4.
  7. Repeat experiment with a variety of weight in the box.
  8. Ask students what happened to the rubber band as more weight was added to the box.
  9. Ask the students if the force needed to be stronger or weaker with the added weight.
  10. Ask when have the students experienced a time when weight made it harder to move an object (riding a bike with two people, pulling a wagon full of rocks).

 

 

Dr. Robert Sweetland's notes
homeofbob.com & schoolofbob.com