So So Stuck

[stephanieteddy]

I am dying with the Kinematics and Dynamics chapters. My non-physics background is biting me in the bum and it hurts!

Can someone please please help me with the following question from Essential Maths 13A

I have no idea why the solutions do what they do.

Q 18 The angles between the forces of magnitude 8 N, 10 N and P N are, respectively, 60◦ and
90◦. The resultant acts along the 10 N force. Find P.

Solutions are: || 10 N: 10 + 8 cos 60° = 14 N
⊥ 10 N: 8 sin 60° – P
∴8 sin 60° – P = 0
∴P = 8 sin 60°
= 4 3 N
≈ 6.93 N

But whyyyyy

[stephanieteddy]

Please help me

[Jenny_2108]

I am dying with the Kinematics and Dynamics chapters. My non-physics background is biting me in the bum and it hurts!

Can someone please please help me with the following question from Essential Maths 13A

I have no idea why the solutions do what they do.

Q 18 The angles between the forces of magnitude 8 N, 10 N and P N are, respectively, 60◦ and
90◦. The resultant acts along the 10 N force. Find P.

Solutions are: || 10 N: 10 + 8 cos 60° = 14 N
⊥ 10 N: 8 sin 60° – P
∴8 sin 60° – P = 0
∴P = 8 sin 60°
= 4 3 N
≈ 6.93 N

But whyyyyy

why is the solution so long?
I just do 8/sin90=P/sin60 => P=8sin(60)=6.93N

[Hutchoo]

I think for that question it wanted you to use resolving forces? [like it actually says "use resolving forces for the following questions"]

IF IT DIDN'T, then just use lami's theorem (as jenny did)