Tension Homework Answer Key

Since the person is exerting a force of 7 N onto the string, we can use that force as a vector. The direction is towards the person since they are pulling the string towards them and the magnitude of the vector is 7.

Since we know two sides, the adjacent side and the hypotenuse side, you would use the cosine trig identity: cosθ = adjacent/hypotenuse

Since N (a neuton) is equal to (kg*m)/(s)², or kilogram meter per second squared, you would have to change the 10 cm into meters for the units to match.

Now we have the adjacent side: 10cm * (1m/100cm) = 0.1meters

And we have the hypotenuse side: 7 (kg*m)/(s)²

And the units match so you can plug in the values and calculate theta:

cosθ = 0.1/7

cosθ = 0.0143…

cos-1 will give you the angle at which the person is holding the string

Now we have that θ = 89.18˚