Question

Newton's Laws.
The only two forces acting on a body have magnitudes of 20N and 35N and their directions differ by 80 degrees. The resulting acceleration has a magnitude of 20 m/s^2. What is the mass of the body?
I have a solution but I don't understand it. Could someone go over this with me?

Answer 1

@IrishBoy123 @jiteshmeghwal9

Answer 2

Step 1: draw the forces

Step 2: use either one of the force directions as the x -axis or y-axis, then go to Step 3. [in the drawing, we use the 20N direction as the x-axis ]

Step 3: resolve forces in x and y directions

Step 4: work out the net force using Pitagoras Theorem

Here you should get

\(F_{net} = \sqrt { (20 + 35 \cos 80 )^2 + (35 \sin 80)^2 } \)

And then whack it with...

\(F_{net} = m a\)


Ta-Da!!

;-)

Answer 3

Okay, I think my problem was the way I was drawing my diagram made it difficult to understand the forces (with the idea of gravity clouding my brain). I'll see if I can get it. Thanks!