Newton's second law of motion!!!?????!!!?

Question

I am having trouble understanding the second law of motion. Can someone explain it in their own words please?? That would be great. I have to know it for a physics test tommorrow...

Please do not just google the topic and copy and paste a weblink or anything from the web. I have read a lot of websites but i still don't get it.

Thanks

Answer 1

Let's say you get hit by a car.

However the car is moving at 0.05 mph, therefore when it contacts you you are not injured. Why? not much force!

Yes, the mass of the car is large but the force is very small because the large mass was multiplied by a very tiny deceleration when the car stopped.

Now let's say you are whacked by a tennis ball served at 120 mph by a tennis pro. Oww! it hurts. Yet you are not injured. Why? Because though the deceleration is a lot (because it was moving so fast) it is multiplied by only a small mass.

Now imagine you are tackled by a NFL linebacker. When you wake up in the hospital Dr. Newton stops by to explain that the player's rather large mass was multiplied by a large deceleratoin on impact. (In other words he was a big guy moving fast, otherwise he wouldn't be in the NFL in the first place.)

Ever seen a first grader go bowling? The ball rolls slowly down the lane and barely nudges the pins. Not much action!
How about a good bowler? Plenty of pin action. Why? More mass from a heavier ball multiplied by a lot more deceleration. How much more force? Let's say the ball is 3 times heavier than the first grader's ball. Plus it is moving 10 times faster! How much more force does it have??

(Hint: 3 X 10 = 30)

Yes, it has 30 times more force!

One more example:
You try to push a car into someone's driveway. Your pushing force is not going to accelerate that car very much is it? Because the car has so much . . . MASS! When your force is divided by the car's large mass you get a tiny acceleration. Fortunately you're not in the Indy 500, just in the driveway. However if you push first grader on his bike (he's done bowling) with the same force that you mustered for the car, you are going to be in danger of pushing him over. Why? Not much mass for your large force, so you get a lot of acceleration. First grader goes crying to Mom that you almost pushed him over.

Plus you dropped a bowling ball on his foot. i forgot to mention that.

Answer 2

Force = mass * acceleration You can rearrange that equation however you need to to solve for the missing parameter. In this case, you know the initial Force (63 N) and the acceleration (9 m/s^2). You put the knowns on the same side of the equation: (63 N) / (9 m/sec^2) = mass = 7 kg Now you have a new force on the same object (mass stays constant), so you have to rearrange the F=ma equation to put your knowns on the same side of the equation: (28 N)/ (7 kg) = acceleration = 4 m/sec^2 If you're doing dimensional analysis, it would help to know that 1 N = (1 kg m)/sec^2. It helps as a double check to make sure you did your algebra correctly when you're moving your knowns to the same side of the equation.

Answer 3

Newton's Second Law of Motion:

Force = Mass X Acceleration
F = ma

In this case, the force is written as (kg*m/s^2) or simply as N, standing for Newtons. This law is basically used to find how much force is applied to an object depending on its mass an size.

In this equation, acceleration is inversely proportional to the mass, meaning that if the mass were to double, the acceleration would be halved. The same applies to the mass.

I'm not sure what you don't understand, can you be more specific?

Answer 4

From what I recall is that
Force = mass x acceleration
In that the force is directly proportional to the mass of the object and its acceleration
And from that the
acceleration = force / mass
which shows that if the force increases the acceleration increases and if the mass increases then the acceleration of the object will decrease.

Answer 5

This seems to be so clear an explanation, with practice exercises, that even a non-physics person like me might be able to understand it with a modicum of exertion.

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l3a.html

If this or another answer here proves helpful in your research, you can encourage good answers by choosing one answer as the "best answer."

Cheers,
Bruce