# Hw Help

#### i2hckynut18

Hw Help!!!!

I'm struggling with 3 problems, can anyone help me out?

(1)You are riding on a jet ski at an angle upstream on a river flowing with a speed of 2.8 m/s. Suppose the jet ski is moving at a speed of 11 m/s relative to the water.

At what angle must you point the jet ski if your velocity relative to the ground is to be perpendicular to the shore of the river?

(2) Initially, a particle is moving at 4.80 m/s at an angle of 35.0° above the horizontal (+x axis). Two seconds later, its velocity is 5.45 m/s at an angle of 50.0° below the horizontal. What was the particle's average acceleration during this time interval?

(3) A football is thrown horizontally with an initial velocity of (16.2 m/s). Ignoring air resistance, the average acceleration of the football over any period of time is (-9.81 m/s2).

(a) Find the velocity vector of the ball 1.81 s after it is thrown.
= ( m/s)x - ( m/s)y

(b) Find the magnitude and direction of the velocity at this time.
Magnitude ____m/s
Direction ___° below horizontal

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#### semc

for qn 2&3 jus use the EOM in both the x n y direction to get the ans

#### i2hckynut18

not to sound like a complete idiot, but the EOM? i think i'm officially the worst person in the world at physics!!!!

#### HallsofIvy

I think "EOM" means 'equation of momentum' and semc is really referring to "conservation of momentum".

#### arunbg

Hmm, more like equations of motion

#### Farsight

i2hckynut18: all this is easy. Try drawing some triangles.

#### semc

ya actually i mean equation of motion like v=u+at

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