Materials

Wireless Dynamics Sensor with small eyehook and large eyehook attached

Laptop with Bluetooth dongle

Mass Hanger

Gram mass set

Short piece of string with a loop

Introduction

In this activity, we will explore Newton’s 1st law. We will lift a force on a sensor at a constant velocity and measure the net force acting on the sensor.

Procedure

1. Connect the Sensor

Start up LoggerPro. Turn on the Wireless force probe. In LoggerPro click on the Experiment menu, the click on Connect Interface, then click on Wireless and then click on Scan for Wireless Devices. LoggerPro will think for a minute or two and then give you a message box saying it couldn’t find any devices. Click on Yes to scan again and after a little bit, LoggerPro should give a list of the wireless sensors it found. Make sure that the box is checked that matches the name on your sensor, and no other. If you don’t get the list of available sensors at this point contact your instructor. Make sure that the small eye hook is screwed into the force probe on the sensor.

2. Open the Experiment file. Click on the open icon . Double click on the Probes & Sensors folder and then double click on the WDSS folder. (You will have to scroll over to find it.) Double click on the Newton II file.

3. Zero the Probe

Place the loop of string around the small eye hook and suspend the sensor vertically by the string. Suspend the sensor vertically by the string. Try not to let the sensor swing back and forth. Click on the Zero button . Make sure that the Force and acceleration boxes are checked and click OK. The sensor will now read the net force exerted on the sensor. You should Zero the sensor in the same way each time before taking data

Q1) What forces are acting on the sensor? Hint: If you released the sensor, what would happen?

Q2) Draw a diagram showing the forces acting on the sensor. Forces are vectors so you should draw them as arrows.

Q3) What is the net force acting on the sensor when it is suspended vertically from the string at rest?

4. Data Collection

P4) If you raise the sensor at a constant velocity, will a net force be exerted on the sensor? Explain.

We’ve adjusted the force probe so that it reads the net force on the sensor. If the net force is upwards it will read a positive force, and if the net force is downwards it will read a negative force.

Click on the collect button and while maintaining the force probe in the same orientation slowly raise it a constant velocity.

Examine the graph of Force vs. time and answer the following.

Q5) Was there a slight acceleration when the sensor started moving?

Q6) Did you exert a net force to get the sensor moving?

Q7) Once the sensor was moving at constant velocity, was there an acceleration?

Q8) Once the sensor was moving at constant velocity was there a net force exerted on it?

Now repeat the procedure, but raise the sensor with a greater constant velocity.

Examine the graphs of Acceleration vs. time and Force vs. time and answer the following.

Q9) Was there a slight acceleration when the sensor started moving?

Q10) Did you exert a net force to get the sensor moving?

Q11) Once the sensor was moving at constant velocity, was there an acceleration?

Q12) Once the sensor was moving at constant velocity was there a net force exerted on it?

Repeat the procedure again, but this time lower the force probe with a constant velocity.

Examine the graphs of Acceleration vs. time and Force vs. time and answer the following.

Q13) Was there a slight acceleration when the sensor started moving?

Q14) Did you exert a net force to get the sensor moving?

Q15) Once the sensor was moving at constant velocity, was there an acceleration?

Q16) Once the sensor was moving at constant velocity was there a net force exerted on it?

Repeat the procedure again, but lower the sensor with a greater constant velocity.

Examine the graphs of Acceleration vs. time and Force vs. time and answer the following.

Q17) Was there a slight acceleration when the sensor started moving?

Q18) Did you exert a net force to get the sensor moving?

Q19) Once the sensor was moving at constant velocity, was there an acceleration?

Q20) Once the sensor was moving at constant velocity was there a net force exerted on it?

S21) In all of the above cases, when the sensor moved at a constant velocity, what was the net force acting on it?

Galileo first understood this idea and Newton adopted as his first law of motion which states:

An object at rest remains at rest and an object in uniform motion remains in uniform motion unless a net force acts on it.