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Physics IGCSE question Newton's Laws

question from edexcel Physics IGCSE:
"The figure below shows the forces acting on a child who is balancing on a pogo stick.
The child and pogo stick are not moving. ...

a) The downward force of the child on the spring is equal to the upward force of the spring on the child.
This is an example of which one of Newton's Laws of Motion?"

The correct answer was the Third Law, but surely the First also applies here considering the objects are "not moving"?

Stubborn and pedantic question to ask, but I really don't see why the First Law is incorrect here.
Thank you
Reply 1
Original post by LionTSR
question from edexcel Physics IGCSE:
"The figure below shows the forces acting on a child who is balancing on a pogo stick.
The child and pogo stick are not moving. ...
a) The downward force of the child on the spring is equal to the upward force of the spring on the child.
This is an example of which one of Newton's Laws of Motion?"
The correct answer was the Third Law, but surely the First also applies here considering the objects are "not moving"?
Stubborn and pedantic question to ask, but I really don't see why the First Law is incorrect here.
Thank you

Hi, just did Edexcel iGCSE physics and I assume this because the third law is about the interaction between two objects: the child is at rest because the force of the spring against the child is equal and opposite
(edited 2 months ago)
Reply 2
Hi, just did Edexcel iGCSE physics and I assume this because the third law is about the interaction between two objects: the child is at rest because the force of the spring against the child is equal and opposite

The first law is incorrect I believe because it is more about the forces exerted upon an object, but here the child is exerting the force and stimulating an equal and opposite force from the spring. Hope that helps. I would really appreciate if you can rep (thumbs up) the post above because it helps me reach my badges target.
Original post by LionTSR
question from edexcel Physics IGCSE:
"The figure below shows the forces acting on a child who is balancing on a pogo stick.
The child and pogo stick are not moving. ...

a) The downward force of the child on the spring is equal to the upward force of the spring on the child.
This is an example of which one of Newton's Laws of Motion?"

The correct answer was the Third Law, but surely the First also applies here considering the objects are "not moving"?

Stubborn and pedantic question to ask, but I really don't see why the First Law is incorrect here.
Thank you


Third law is right: When the child on the pogo stick springs around, there are two equal forces opposed in directions. Before the spring of the pogo stick bounces and moves up into the air, the pressed spring spends a force in direction of the soil what causes a counterforce (to the air). This counterforce rises the stick.
(edited 2 months ago)

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