### Bumpy ride

#### Description of activity

Students are challenged to investigate which surface will make a toy car travel the greatest distance.

They will design and carry out an experiment to find an answer to this problem.

The suggested time for this activity is approximately 1 hour.

#### Context

Students will have discussed that a force can be described as a push, a pull or a twist. They have identified examples of pushes and pulls that affect movement.

Friction is a force that occurs between two surfaces. It is a force that opposes movement. It causes objects to slow down and stop. Different types of surfaces create different amounts of friction. There are two main factors that will influence the total amount of friction:

- the roughness of the surfaces
- the force between the two objects.

#### Outcomes

**Skills**

**Knowledge and understanding**

#### Resources

- Toy cars
- A standard ramp, eg hot wheels ramp, wooden ramp or cardboard ramp
- Areas with different surface coverings, eg carpet, wood, vinyl, plastic, grass, concrete
- Equipment for measuring standard and/or non-standard units of length
- Template of a table for recording data
- Grid paper or simple graphing software

#### Work, health and safety

Check relevant Work, health and safety guidelines.

#### Evidence of work for assessment purposes

- Photograph(s) showing the experimental set up with a description of what was done
- A record of results containing a table and a picture graph
- A statement relating the type of surface to the distance travelled by the car

#### STEM teaching and learning activities

- Students explore their surroundings to find a range of different surfaces to test, noting their texture.
- Students predict which surface will make the car stop quickest or travel the furthest.
- Students discuss that friction is a force that exists whenever two surfaces rub against each other.
- Students explore the effect of different surfaces on the movement of toy cars and predict the effect that the surface texture will have on the movement of the car.
- Students devise experiments to test their predictions. For example, they might suggest that the car would travel further on a wooden surface than on a carpeted one. Students write a prediction and display it clearly.
- Students carry out their experiments in pairs or small groups.
- Students measure the distance travelled by the toy car in standard or non-standard units such as straw lengths.
- Students are provided with a table to record results. See Constructing and using tables.
- Teachers graph the data by hand or use simple graphing software to enter the data and generate a graph. Enter the type of surface on the X (horizontal) axis and the corresponding distance travelled on the Y (vertical) axis. In this case a column graph would be used because the surfaces are different. See Constructing and using graphs.
- Students analyse the chart of data and refer to their original predictions. Does their data support or disprove their predictions?
- Students formulate a conclusion relating the effect of friction on the movement of a car.
- Students compare the results obtained by different groups. Did the results support those gained by different groups? If so, we are more likely to believe the results. If the results are not similar to each other, ask the students how they carried out the experiment as there may have been significant differences that would account for the different results.
- Students suggest ways in which they could improve the design of their experiment, so that their results could be more consistent and reliable.

#### Vocabulary list

**Force** – a push, pull or twist**Friction** – a force that opposes motion**Surface** – the outermost layer of an object**Texture** – the feel or look of an object or substance**Distance** – the length between two points**Data** – facts or figures that can be used to draw conclusions**Table** – a set of facts or figures displayed in columns and rows**Graph **– a diagram showing a relationship between two variables**Results** – information gained from an investigation or completing a calculation**Gravity** – non-contact force

#### Additional information

**The following statements outline some common preconceived ideas that many students hold, which are scientifically inaccurate and may impede student understanding.**

**Every object contains a force**Objects do not 'contain' forces. Forces 'act' upon objects. This confusion is generally about the mass or weight of an object. For example, the heavier an object, the more force it can exert. This is actually true, but the 'force' is the effect of gravity on the mass of the object.

**Only one force acts on an object**Students may realise that gravity is acting on a ball rolling down a hill, but may not consider the effect of friction acting in the direction opposite to the motion of the ball.

**If an object is not moving, there are no forces acting on it**If an object is stationary on the ground, gravity is acting downwards and an opposite and equal force from the ground is acting upwards. If the force of gravity were greater than the upward force, the object would sink into the ground.

**If an object is moving, there is force acting on it in the direction it is moving**If an object, such as a toy car, is given a push across a flat surface, there is initially a forward force acting on it, but once it is allowed to move freely, there is no forward force. Friction exerts a force in the opposite direction to the object’s motion and when the force of friction equals the forward force the toy car will slow and eventually stop moving. Changes in movement, such as starting, stopping or changing direction, happen because of unbalanced forces. Objects will remain moving at a constant speed (even if that speed is 0 m/s) and in a constant direction, when opposing forces are equal to each other or no other forces are acting on the object, eg when the object is drifting through space.

**Forces can only be applied by living things**Students often realise that a human can apply a force but may not consider other forces such as gravity or friction or electro-magnetism.

**It is not necessary to compare data from different groups**Comparing data from different groups is like repeating an experiment. The more times you get the same or similar results, the more reliable your data and your hypothesis as to why something happens.

#### Support material

Friction is a Force: teacher support

**Student activities**

- What is friction – read and complete the activities and quiz
- Friction experiment
- Digger and the Gang: Science – Stuck on Tracks

#### Adjustments for the diversity of learners

Challenge students to think about how they would ensure that the toy car was given the same initial push each time on each surface. One approach might be to use a ramp of a standard height that can be moved to each surface. See the related STEM Activity Ramp it up. Discuss with students what makes the difference to how far the toy car travels from the bottom of the ramp.

Discuss:

- height of ramp
- how far up the ramp the car starts
- surface of ramp
- method of releasing the car.

How would you test these ideas?

Does the mass of the car make a difference?

#### Review

In this STEM activity, your students developed the concept of balanced and unbalanced forces. This is revisited in Science Stages 4 and 5 and forms the basis of understanding Newton’s three Laws of Motion found in Science Stage 5 and Physics Stage 6. Students are also developing the skills of hypothesising, planning and carrying out an investigation as well as collecting, displaying and analysing data to draw logical scientific conclusions.