Original Project
Force and Motion
Item FM089002: A sled that is being pulled with a constant force can move faster than the person pulling it if the force of the pull is greater than the force of friction on the sled.
A boy is pulling a sled with a rope on level ground covered with snow. Assume he is running at constant speed and pulling on the rope with constant force.
Could the sled move faster than the boy is running?
- Yes, but only if he wasn’t running fast.
- Yes, but only if the force of the pull on the sled was greater than the force of friction on the sled.
- Yes, but only if he was pulling the sled downhill and gravity was helping make it go faster and faster.
- No, because if he was pulling with constant force, the sled would have to move at a constant speed.
- Distribution of Responses
- Students Responding Correctly
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 388 | 1722 | 23% |
| Grades | |||
| 6–8 | 238 | 1101 | 22% |
| 9–12 | 149 | 620 | 24% |
| Gender | |||
| Male | 178 | 844 | 21% |
| Female | 207 | 854 | 24% |
| Primary Language | |||
| English | 354 | 1590 | 22% |
| Other | 27 | 97 | 28% |
- Disciplinary Core Ideas
- PS2.A The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.
PS2.A Newton's second law accurately predicts changes in the motion of macroscopic objects.