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AQA GCSE · Question 02.4 · Forces
The child pushed the baby walker from a carpet onto a hard floor. The child applied the same horizontal force to the baby walker. Explain why the speed of the baby walker increased.
The child pushed the baby walker from a carpet onto a hard floor. The child applied the same horizontal force to the baby walker. Explain why the speed of the baby walker increased.
How to approach this question
1. Think about the forces acting horizontally on the walker: the push force from the child and the friction force from the floor.
2. How does the friction of a hard floor compare to a carpet?
3. The resultant force is the difference between the push force and the friction. How does the resultant force change?
4. According to Newton's Second Law (F=ma), what is the relationship between resultant force and acceleration?
Full Answer
Moving from carpet to a hard floor reduces the frictional force. Since the applied force remained the same, the resultant force on the walker increased. According to F=ma, an increase in resultant force causes an increase in acceleration, which means the speed increased.
The motion of the baby walker is determined by the resultant force acting on it. This is the difference between the forward push force from the child and the backward resistive force of friction.
1. **Friction:** A hard floor has a lower coefficient of friction than a carpet. Therefore, the frictional force opposing the motion is smaller on the hard floor.
2. **Resultant Force:** The child applies the same forward force. Because the backward frictional force is now smaller, the overall resultant force (Push Force - Frictional Force) is larger.
3. **Acceleration:** According to Newton's Second Law (F=ma), acceleration is directly proportional to the resultant force. A larger resultant force causes a greater acceleration, meaning the walker's speed increases more quickly.
Common mistakes
✗ Only stating that hard floors are "smoother" without mentioning friction.\n✗ Forgetting to link the change in friction to a change in the resultant force.\n✗ Not mentioning acceleration as the reason for the speed increase.
Practice the full AQA GCSE Physics Higher Tier Paper 2
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