Solve More Force Problems: Mass Calculation

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The discussion focuses on calculating the mass of a body subjected to two forces of 20 N and 36 N, which are at an angle of 72° to each other, resulting in an acceleration of 20 m/s². Participants emphasize the importance of using vector addition and trigonometry to find the resultant force rather than simply adding the magnitudes. The correct approach involves calculating the x and y components of the 20 N force and then applying the Pythagorean theorem to find the resultant force. Newton's second law, F=ma, is then used to determine the mass by dividing the resultant force by the acceleration. The thread concludes with a clarification that breaking the forces into components may not be necessary for this specific problem.
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[SOLVED] more force problems

1. The only two forces acting on a body have magnitudes of 20 N and 36 N and directions that differ by 72°. The resulting acceleration has a magnitude of 20 m/s2. What is the mass of the body?



2. F=ma



3. My original attempt was to add the two force magnitudes and divide by the acceleration magnitude, but I knew that wasn't right. I tried breaking up the force magnitudes up into x,y components, but that didn't seem to work either. So I'm pretty clueless. I'm having a hard time understanding this chapter so far. Hints to point me in the right direction would be great. Thanks.
 
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You can't just add the magnitudes together.

Try using vector addition and some trig to find the magnitude of the resultant force.
 
Let's determine that 36N is on x-axis. Then find x and y components of 20N, which is 20cos(72) and 20sin(72).
Add the x components and 36N together because both are on same direction and axis.
Find magnitude of the force by use pyth. theorem.
Then apply it to Newton's second law, F=ma. Then divide the acceleration, 20 m/s^2, and you will get the mass of the body.
 
snoggerT said:
1. The only two forces acting on a body have magnitudes of 20 N and 36 N and directions that differ by 72°. The resulting acceleration has a magnitude of 20 m/s2. What is the mass of the body?

2. F=ma

No need to break up into x and y components this time. You need only the magnitude.

R^2 = P^2 + Q^2 + 2PQcos(theta), where R is the resultant.
 
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