All basic motion problems involve three elements: rate, time, and distance.
Rate is expressed as a ratio of distance and time, with two corresponding units. Some examples of rates include: 30 miles per hour, 10 meters/second, 15 kilometers/day.
Time is expressed using a unit of time. Some examples of times include: 6 hours, 23 seconds, 5 months.
Distance is expressed using a unit of distance. Some examples of distances include: 18 miles, 20 meters, 100 kilometers.
You can make an “RTD chart” to solve a basic motion problem. Read the problem and fill in two of the variables. Then use the RT = D formula to find the missing variable. For example:
If a car is traveling at 30 miles per hour, how long does it take to travel 75 miles?
| Rate (miles/hr) |
× | Time (hr) |
= | Distance (miles) |
|
| Car | 30 mi/hr | × | = | 75 mi |
An RTD chart is shown here Fill in your RTD chart with the given information. Then solve for the time:
30t = 75, or t = 2.5 hours