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AQA GCSE · Question 02.1 · Forces
A child is standing still in a baby walker. What is the resultant vertical force on the child? Give a reason for your answer.
A child is standing still in a baby walker. What is the resultant vertical force on the child? Give a reason for your answer.
How to approach this question
1. Recall Newton's First Law. What does it say about objects that are stationary or moving at a constant velocity?
2. If an object is not accelerating, what can you say about the forces acting on it?
3. Apply this to the vertical forces on the child.
Full Answer
Resultant vertical force = 0 N.
Reason: The child is stationary / not accelerating, so the forces acting on them must be balanced. The upward force from the floor is equal and opposite to the downward force of their weight.
According to Newton's First Law of Motion, an object at rest stays at rest unless acted upon by a resultant force. Since the child is standing still, their acceleration is zero. From Newton's Second Law (F=ma), if the acceleration (a) is zero, the resultant force (F) must also be zero. This means all the forces acting on the child are balanced. The downward force of weight is perfectly cancelled out by the upward support force from the baby walker and the floor.
Common mistakes
✗ Stating that the resultant force is equal to the child's weight. This would mean the child is accelerating downwards.\n✗ Giving a reason like "gravity is pulling them down" without mentioning the balancing upward force.\n✗ Confusing resultant force with one of the individual forces acting.
Practice the full AQA GCSE Physics Higher Tier Paper 2
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