| |
The main idea of this law depends on two variables; the net force acting upon an object and the mass of the object. This law is also about the acceleration on an object. Sir Isaac Newton described acceleration as being directly proportional to the net force of the
object, and inversely proportional to the mass of the object. These two terms are different. Having something being directly proportional to something means whatever you do to one thing; you have to do the same thing to the other. For example, if I double one thing,
then I double the other. If I halve something else, then I will halve the other. Newton’s 2nd law describes the acceleration of an object to be directly proportional to the net force acting upon the object. In other words, if I double the net force, then I double the
acceleration etc. On the other hand, if something is inversely proportional then it means the opposite happens. In other words if you double one thing, then you halve the other. If you halve one thing you double the other.
In this law, Newton describes the acceleration of an object to be inversely proportional to the mass of the object. Basically this means that if the mass is doubled, then the acceleration will be halved. If the mass is halved then the acceleration will be doubled.
This law basically states that unbalanced forces cause objects to accelerate with an acceleration which is directly proportional to the net force acting upon the object, and inversely proportional to the mass of an object.
A useful equation to have when using the 2nd law is:
Net force = mass * acceleration …………. Fnet = m * a
EXAMPLE
If an object is accelerating at 6m/s/s and the net force is doubled and the mass is halved, what will the acceleration be?
You would have to double 6 (as acc. is directly proportional to the net force), and then double this answer (as acc. is inversely proportional to the mass of an object. |
|
Imagine yourself pushing a crate carrying 5 pars of shoes along a smooth path. If another 5 pairs of shoes were added to the crate, then the mass is doubled. Because the mass is inversely proportional to the acceleration, the acceleration of the crate carrying 10
pairs of shoes would be halved. If you take out the 5 pairs of shoes again, then the mass will be halved, therefore the acceleration will be doubled. |
| |
Two people are going parachuting; a man and a woman. The man is both taller and heavier than the woman, therefore giving him a bigger surface area. They both jump out of a plane at the exact same time but they land at different times. This is due to the size of the
individuals. Because the man has a larger surface area than the woman, he is acted upon by a larger force of gravity. This means he will accelerate at a higher speed until the force of air resistance equals his force of gravity. This means it took longer for the
woman to reach the ground than it did the man. |
