# Help with vectors for physics homework?

2. Consider the two vectors,

A = 16.5x + 35.5y

B = 5.7x - 21y

2. A) What is the magnitude of the vector A - B?

I already found the answer to this, 57.5, but can't figure out the rest

2. B) What is the angle of the vector A - B, measured counterclockwise in degrees from the positive x-axis?

2. C) What is the magnitude of the vector 3A + B?

2. D) What is the angle of the vector 3A+B, measured counterclockwise in degrees from the positive x-axis?

### 2 Answers

- VamanLv 78 months ago
A = 16.5x + 35.5y

B = 5.7x - 21y

A-B= (10.8, 56.50) Magnitude =sqrt(10.8^2+56.5^2)=57.5

magnitude A=39.15, B=21.75.

cos a= A dot B/(AB)=0.06. a=1.51 degrees

Rest you can do.

- ?Lv 78 months ago
A-B = <10.8 , 56.5>

b/

angle θ , with tan(θ) = 56.5/10.8 ---> θ = 79.2 degrees

c/

3A+B = 3<16.5, 35.5> + <5.7 , -21> = <55.2 , 85.5>

--> ||3A+B||=101.8

d/

tan(θ) = 85.5/55.2 ---> θ = 57.2 degrees