The first step in solving a physics problem is to draw a pricture

2008-03-30T16:21:00.000-07:00

Have you been told the first step in solving a physics problem is to draw a picture, but how do I draw a picture and why. The main reason to draw a picture is to aid you to convert a word problem to symbols. This method is called the pictorial representation of the problem.

Here is the list of thing that goes into the pictorial representation:
1. Sketch the situation. Show the object at the beginning of the motion, and at any point where the character of the motion changes. Keep the drawing simple.
2. Establish a coordinate system. Your axes and origin should match the motion.
3. Define symbols. Use the sketch to help you define symbols that will represent the quantities such as position, velocity, acceleration and time. Remember that these symbols will be use in the mathematical solution for the problem.
4. List known information. As you read the problem look for quantities whose values are stated in the problem or that can be found with simple geometry or unit conversion. Also some quantities are implied by the problem, rather than explicitly stated. As other may be determined by your choice of coordinate system.
5. Identify the desired unknowns. As you read the problem note what quantity or quantities will allow you to answer the question or questions. These should been defined as symbols in step 3. You do not need to list every unknown only the one or two needed to answer the question.
Remember a well done pictorial representation of the problem will take you halfway to the solution.

Problem: 1.1 A car accelerates from a stoplight at 5.0 m/s/s for five seconds, then coasts for three more seconds. How far has it traveled?

Problem: 1.2 A ball roll along a smooth horizontal floor at 10 m/s, then starts up a 20o ramp. How high does it go before rolling back down?

Problem: 1.3 A train start from rest and moves with constant acceleration. On first observation the velocity is 10 m/s and 40s later the velocity is 40 m/s. At 40s, calculate the position, velocity, and acceleration over the given time interval.

Dr. Evans' Physics Helper

The first step in solving a physics problem is to draw a pricture