Edexcel IGCSE Physics 复习笔记 1.1.3 Core Practical: Investigating Motion

Aim of the Experiment

• The aim of this experiment is to investigate the motion of some everyday objects, such as:
  • A paper cone
  • A tennis ball

   

• This is just one method of carrying out this experiment - some methods involve the use of light gates to measure speed and acceleration, e.g. for a toy car moving down a slope

Variables:

• Independent variable = Distance, d
• Dependent variable = Time, t
• Control variables:
  • Use the same object (paper cone, tennis ball etc.) for each measurement

   

Equipment List

• Resolution of measuring equipment:
  • Ruler = 1 mm
  • Stop clock = 0.01 s

   

Method

Investigating the motion of a falling paper cone

1. Measure out a height of 1.0 m using the tape measure or metre ruler
2. Drop the object (paper cone or tennis ball) from this height, which is the distance travelled by the object
3. Use the stop clock to measure how long the object takes to travel this distance
4. Record the distance travelled and time taken
5. Repeat steps 2-3 three times, calculating an average time taken for the object to fall a certain distance
6. Repeat steps 1-4 for heights of 1.2 m, 1.4 m, 1.6 m, and 1.8 m

• An example table of results might look like this:

Analysis of Results

• The average speed of the falling object can be calculated using the equation:

• Where:
  • Average speed is measured in metres per second (m/s)
  • Distance moved is measured in metres (m)
  • Time taken is measured in seconds (s)

   

• Therefore, calculate the average speed at each distance by dividing the distance by the average time taken

Evaluating the Experiment

Systematic Errors:

• Make sure the measurements on the tape measure or metre rule are taken at eye level to avoid parallax error
• Consider using an electronic sensor, such as light gates, to obtain highly accurate measurements of time
  • Once the object is released, the timer starts and stops automatically as it reaches the sensor on the ground

   

Random Errors:

• Ensure the experiment is done in a space with no draught or breeze, as this could affect the motion of the falling object
• Using a ball bearing and an electronic data logger, like a trap door, is a good way to remove the error due to human reaction time for this experiment

Safety Considerations

• Place a mat or a soft material below any falling object to cushion its fall

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