For example, a ball thrown onto the ground exerts a downward force; in response, the ground exerts an upward force on the ball and it bounces.
A person is unable to walk on the ground without the ground’s frictional force. When he takes one step forward, he exerts a backward force on the ground. The ground responds by exerting a frictional force in the opposite direction allowing the walker to move forward as he takes a further step with his other leg.
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Answer:
For example, a ball thrown onto the ground exerts a downward force; in response, the ground exerts an upward force on the ball and it bounces.
A person is unable to walk on the ground without the ground’s frictional force. When he takes one step forward, he exerts a backward force on the ground. The ground responds by exerting a frictional force in the opposite direction allowing the walker to move forward as he takes a further step with his other leg.