# Physics: Vectors, velocity.?

2. Find the x and y components of the force vector shown in the figure

below. “A” designates the length of the arrow.

3.Three vectors A,B, and Chave the following components: Ax= 5.00, Ay=7.00; Bx= 4.00, By= -3.00; Cx= -2.00, Cy= 5.00.

(a) Find the x and y components of A+B+C.

(b) Find the magnitude and direction of A+B+C.

4.Standing on a balcony, you throw your keys to a friend standing on the ground below. One second after you release the keys, they have an instantaneous velocity of 13.9 m/s, directed 45° below the horizontal. What initial velocity did you give them?

### 1 Answer

- NCSLv 72 months agoBest Answer
2. The angle is given w/r/t horizontal, so

Ax = A*cos45.0º

Ay = A*sin45.0º

3. C'mon, you can do this.

x = Ax + Bx + Cx

y = Ay + By + Cy

mag |A+B+C| = √(x² + y²)

direction Θ = inverse tan(y/x)

4. horizontal velocity Vx = 13.9m/s * cos45º = 9.83 m/s

at all times

and at that moment,

Vy = 9.83 m/s down.

So at release,

Voy = Vy - g*t = 9.83m/s - 9.8m/s²*1s = 0.0188 m/s

which is basically 0 m/s.

So you initially threw them at 9.83m/s and horizontally.

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