If i push an object with a small mass/inertia with as much force as i can exert, such as a physics textbook, is this object exerting an equal and opposite force on me? Because unlike when i push a heavier object like a table, i do not get pushed back or feel the equal or opposite force.
Answer
Newton's Law still holds here. The reason that you do not feel much force from the object is that you are not exerting much force on it in the first place.
Your hand and arm have mass, and your muscles have a maximum output. You can only accelerate your hand so fast, even when it's completely empty.
Light objects take very little force to create large accelerations. For something light like a feather or a grain of rice, the force required to accelerate as fast as your empty hand is tiny. The coupled force back onto your hand is also tiny and possibly below the threshold of detection.
Let's be optimistic and consider you might be able to accelerate your hand at a huge rate like $10g$. That then means the accelerating force (and also the force back onto your hand) from any object is about 10 times greater than its weight. A single feather would push back with the weight of 10 feathers. Still such a small amount that you would have trouble noticing.
To really notice, you might need to accelerate it at more like $100$ or $1000g$, and that's just not something your muscles can do to your hand.
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