welcome to the Dashi science where our goal is to make science simple please like this video And subscribe to our channel so we can produce more helpful science content motion is all around us in this video we're going to cover the formula for Newton's third law of motion and how to use that formula to solve different practice problems [Music] [Applause] in order to understand how to perform the calculations for Newton's third law it is important that you remember the information we covered in our what is a force video and our Newton's third law of motion video if you don't remember this information or need a refresher please check out our videos on these topics remember Newton's third law states that for every action there's an equal and opposite reaction the formula that we will use is p equals MV where p is momentum in kilograms times meters per second m is mass in kilograms and V is velocity in meters per second we can solve this formula by knowing two of the variables and solving for the Third an easy way to solve this formula is to use the triangle setup shown here when using the triangle all you have to do is cover up the letter you are solving for and the triangle will tell you whether to multiply or divide if I'm solving for momentum I cover up the p and the triangle tells me to multiply mass times velocity I know this because the variables are next to each other if I'm solving for Mass I'll cover up the m and the formula tells me to do momentum divided by velocity I know this because the variable p is on top of the variable V and finally if I'm solving for velocity I cover up the letter V and the triangle tells me to divide momentum by mass and I know this because the variable p is on top of the variable m now let's look at some practice problems our first example the question says a 4 000 kilogram truck travels in a straight line at 10 meters per second what is the momentum so using my triangle I will cover up the letter P because P represents momentum and the question is asking me to solve for momentum so from my triangle I can see that P is going to be equal to mass times velocity and I know that because the m and V are next to each other so I can write my formula P equals MV and then all I need to do is plug in my mass and velocity from the problem so I can plug in the mass of 4 000 kilograms and the velocity of 10 meters per second after that I then just put it in my calculator where I can do 4000 times 10 which gives me a final answer of 40 000 kilograms times meters per second in the next example the question says a beach ball is rolling in a straight line towards you at a speed 0.5 meters per second its momentum is 0.25 kilograms times meters per second what is the mass of the beach ball so looking at my triangle I'll cover up the letter M which tells me to do p divided by V so I can write my formula m equals P divided by V and then I can find the momentum and the velocity from the question and plug those into my formula so I'll put 0.25 divided by 0.5 I can then plug this into my calculator and get an answer of 0.5 kilograms in the final example the question says an eight kilogram bowling ball is rolling in a straight line towards you if his momentum is 16 kilograms times meters per second how fast is it traveling so looking at my triangle I can cover up the letter V and that will tell me to do p divided by m so I can write my formula V equals P divided by m and then all I have to do is plug in the numbers from the problem so I will plug in 16 for p and 8 for m now I can just put this in my calculator and do 16 divided by 8 to get a final answer of 2 meters per second now you know how to solve the equation P equals MV if you found this video helpful please like the video and subscribe to the channel to help us be able to produce more helpful science content if there's a specific topic you need help with please let us know in the comments [Music] foreign [Music]