# Car and Ramp - Student Practice

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## Objective

Students will be able to gather data about the behavior of a car on a ramp as the car accelerates down the ramp.

#### Big Idea

Collecting data to calculate velocity and acceleration can be intimidating for young scientists. This activity is designed as a practice session using the equipment prior to collecting data to calculate velocity and acceleration.

## NGSS Background

This lesson is based on California's Middle School Integrated Model of NGSS.

MS-PS2 Motion and Stability: Forces and Interactions

PE: MS-PS2-2 - Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object.

DCI: PS2.A: Forces and Motion: All positions of objects and the directions of forces and motions must be described in an arbitrary choose reference frame and arbitrary chosen units of size. In order to share information with other people, these choices must also be shared.

Science and Engineering Practices 3: Planning and Carrying Out Investigations - Collect data about the performance of a proposed object, tool, process or system under a range of conditions.

Crosscutting ConceptSystems and System Models - Create a small-scale artificial system isolating variables (distance and time) to calculate real-world measurements, such as velocity and acceleration.

This activity is designed as a practice lesson using CPO's Car and Ramp kit, Physics Stand, and Timer with Photogates. The eventual goal is to have your students calculate the velocity (Car and Ramp - Calculating Velocity) and acceleration of the moving car (Car and Ramp - Calculating Acceleration). Additional practice may be needed in order to calculate velocity (Calculating Velocity Practice) and acceleration (Calculating Acceleration Practice).

The purpose of this lesson is to allow the students time to gather data in a practice setting, using the equipment in a simplified manner, free from intimidating formulas and/or procedures. The students learn to set the equipment up correctly, attach and activate the timer and photogates, roll the car down the ramp, and record the car's time through the photogate. In doing so, they have planned and executed an investigation that demonstrates that an object rolling down an incline increases its velocity and acceleration over time (MS-PS2-2). They use descriptive labels such as centimeters and seconds to describe the distance between photogates and the time the car takes to pass through specified photogates respectively (PS2.a). By collecting this sort of data they are able to eventually calculate velocity and acceleration in a range of conditions that include positions along the ramp, changes in ramp angle, and mass of the car (SP3). By isolating the different variables on a ramp the students can learn basic physics concepts that can be applied in the future to more complex real-world scenarios (CCC).

The order of instruction is as follows:

1. Car and Ramp - Student Practice (this lesson)
2. Calculating Velocity Practice
3. Car and Ramp - Calculating Velocity
4. Calculating Acceleration Practice
5. Car and Ramp - Calculating Acceleration

## Set-up (Prelab)

25 minutes

The following equipment is needed for this activity:

The purpose of this particular activity is to provide experience working with the equipment. The students only record the time (in seconds) the car takes to make it through ONE photogate. They use this equipment to calculate the cars velocity (Car and Ramp - Calculating Velocity) and acceleration (Car and Ramp - Calculating Acceleration) in later activities. An introductory lab, like this, reduces anxiety later on.

The students must be shown how to set-up the equipment.

The stand supports the ramp and the ramp holds the car and the timers with photogates. At the end of the ramp is a wooden foot that elevates the ramp above the ground. Photogates are black clamps that attach to the ramp (see photo above) and plug into the timer, providing a start and stop photo linked to the stopwatch function in the Timer. Photogates project an invisible beam of light that are broken by the car's wing.

The timer is connected to the photogates and displays how long the car takes (in seconds) to travel through the gates. For this activity only one gate is used. When only using one photogate, it must be plugged into the 'A' slot and the timer must be set to 'Interval' (default setting). When the car passes through the 'A' gate the timer displays seconds up to four decimal places. This is the value my students record for this activity.

Weights are added to the car after each race to provide variation to the activity. The wing on the car breaks the invisible light beam on the photogates.

To make it easier to communicate desired ramp positions to my students I numbered the holes on the stand from 1 to 19. When I want all my students to be testing at a specific angle I can tell them to place the ramp on the 'four hole' spot. FUNNY STORY - My eighth graders adopted 'four hole' as their new secret curse word and began using it at lunch. Several of the lunch proctors asked me what a 'four hole' was.

As part of the clean-up procedures the student are shown how to place the timer equipment back inside the storage box, so as to not smash/break any of the equipment.

## Student Activity (Lab)

45 minutes

Pass out Single Photogate Lab - Time versus Position and Single Photogate Lab - Graph to each student. I typically combine these two documents into one packet.

The students first position the ramp at the lowest setting possible to achieve the slowest speed. The slower moving car gives them a better visualization of what they are doing. Remember this activity is about getting to know the equipment, so that they will be able to be proficient enough to calculate velocity (Car and Ramp - Calculating Velocity) and acceleration (Car and Ramp - Calculating Acceleration).

TIP: They will want to immediately place the ramp at the highest setting to get the greatest speed. I let them know that if they can be patient now, I will allow them to place the ramp at the highest setting during a later activity.

Once the ramp is in position. The students set up the Timer and the Photogates. They need only one gate and it needs to be plugged into the 'A' input and the Timer needs to be set to 'Interval' so that it acts as a stopwatch when the car activates the gate. The car was a wing on one side that needs to face towards the photogate.

The students experience a total of twenty races (one race = one timed roll down the ramp). The students have the option of placing the gate at any position they desire. Five positions (five races) are recorded when the car has zero weights attached. Five positions (five more races) are recorded when the car has one weight attached. Five positions are recorded when the car has two weights attached, and so on until the car has three weights attached. NOTE: The maximum weight limit is three weights and each weight weighs approximately five grams.

TIP: I recommend that the students only move the position of the photogates down the ramp in an orderly fashion, stopping at whole number positions (i.e. placing the gate at 50 cm vs. 54 cm). Moving it this way takes less time and using whole numbers makes calculating velocity, in another lab (Car and Ramp - Calculating Velocity), a lot simpler.

The students are only recording the time it takes the car to pass through the photogate. Once they have their twenty measurements they graph their data with Single Photogate Lab - Graph and answer a set of questions.

## Student Reflection (Postlab)

15 minutes

The goal of this activity is to provide experience with the equipment. The students are to only record data and plot that data on a graph. No conclusions are required.

## Extension

50 minutes

If your students need extra instruction for these concepts, I have included two PowerPoint lessons.

Further practice can be found in these two lessons: