1. The car is moving at 60 miles per hour relative to the ground.
2. The person inside the car is stationary relative to the car, so their speed relative to the car is 0 miles per hour.
3. Relative to the ground, the person inside the car is also moving at 60 miles per hour because they are in the moving car.
4. If the person walks forward inside the car at 3 miles per hour relative to the car, their speed relative to the ground becomes 60 + 3 = 63 miles per hour.
5. If the person walks backward inside the car at 3 miles per hour relative to the car, their speed relative to the ground becomes 60 - 3 = 57 miles per hour.
6. The key concept is that motion is relative: an object’s speed depends on the frame of reference from which it is observed.
7. In this case, the two frames of reference are the car (moving frame) and the ground (stationary frame).
8. To find the speed relative to the ground, add or subtract the person’s speed relative to the car from the car’s speed relative to the ground, depending on direction.
Parent Tip: Review the logic above to help your child master the concept of reference point worksheet.
