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P5 R) Newtons Third Law
P5 R) Newtons Third Law
Newton’s third law states that,
“when two objects interact, the forces that they exert on each other are equal and opposite”
We are now going to have a look at two different situations for Newton’s third law.
Equilibrium
The example that we are going to use is an individual pushing against a wall. When an individual pushes against a wall, the wall will push back with an equal and opposite force (this is the normal contact force). The two forces of the individual pushing the wall and the wall pushing the individual back will be equal and opposite to one another. This means that both the wall and the individual remain in the same position – the individual and the wall are in equilibrium.
The example that we are going to use is an individual pushing against a wall. When an individual pushes against a wall, the wall will push back with an equal and opposite force (this is the normal contact force). The two forces of the individual pushing the wall and the wall pushing the individual back will be equal and opposite to one another. This means that both the wall and the individual remain in the same position – the individual and the wall are in equilibrium.
This equilibrium would continue to occur no matter how hard the individual pushed against the wall because the wall will push the individual back with an equal and opposite force. If the individual pushed the wall harder, the wall would push back harder on the individual – the wall will always push back with an equal and opposite force.
As soon as the individual stops pushing the wall, the wall will stop pushing the individual.
As soon as the individual stops pushing the wall, the wall will stop pushing the individual.
Ice Skaters
We are now going to have a look at two ice skaters pushing against each other.
We are now going to have a look at two ice skaters pushing against each other.
When the ice skaters push against each other, they will exert an equal and opposite force on each other; both of the ice skaters experience the same force. After pushing each other, the ice skaters will accelerate away from each other in opposite directions. The acceleration of each of the ice skaters depends on the masses of each of the ice skaters. From the diagram above, we can see that the ice skater on the left has a mass of 60 kg and the ice skater on the right has a mass of 75 kg. From Newton’s second law (f = ma), we know that force and mass are inversely proportional to each other; this means that for the same force, a smaller mass will have a greater acceleration, and a larger mass will have a smaller acceleration. Therefore, the ice skater on the left will accelerate at a greater rate than the ice skater on the right because the mass of the ice skater on the left (60 kg) is less than the mass of the ice skater on the right (75 kg).