Another Two Dimensional motion question

hurtingBrain

1. The problem statement, all variables and given/known data
A second baseman tosses the ball to the first baseman, who catches it at the same level from which it was thrown. The throw is made with an initial speed of 17.0 m/s at an angle of 35.0° above the horizontal. (Neglect air resistance.)

What is the horizontal component of the ball's velocity just before it is caught?

3. The attempt at a solution
i got the time but i keep getting the velocity wrong.

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physicsface

You may be making this too complicated. You're given a vector at an angle of 35 degrees; try finding its components.

hurtingBrain

what do you mean by the compents?

physicsface

The vectors in the horizontal and vertical directions that make up the vector you're given. The vector you're using has a magnitude of 17 m/s, at an angle of 35 degrees to the horizontal. Use trig functions to find the individual components.

hurtingBrain

would you do this?
sin35 = x/17 and solve for x

physicsface

No, the sine helps you solve for the vertical component. Try cosine.

hurtingBrain

cos35 = x/17
than would you use the final speed formula
square root Vx^2+Vy^2

physicsface

You're making it too complicated~

X is your horizontal component here. Solve 17cos35=x and you're done.

hurtingBrain

really thats the velocity

physicsface

Yep. Your original vector is a velocity (speed in a direction), so therefore the component vectors are also velocities.

hurtingBrain

i see, but i always thought that if you throw it x velocity in the begining that it would be the same velocity at the end
and thanks :)

physicsface

But the ball's thrown at an angle. So it'll hit the first baseman's hit at the same speed that it left the second baseman's hand, yes. Assuming the second baseman's hand when the ball leaves it has the same elevation as the first baseman's mitt when he makes the catch. However, the component vectors are a different thing - since you're neglecting air resistance, the horizontal velocity remains the same throughout the throw, but the vertical velocity changes as the ball reaches the peak of its arc.

ANYWAY, USE TRIG FUNCTIONS TO FIND COMPONENTS

hurtingBrain

lol. thanks for the help

No problem :)

hurtingBrain

ah, can you help me on this one too
A swimmer runs horizontally off a diving board with a speed of 3.60 m/s and hits the water a horizontal distance of 1.81 m from the end of the board.

How high above the water was the diving board?

physicsface

Alright, you know the swimmer's horizontal velocity is 3.6 m/s and he travels 1.81 m before hitting the water. You also know that acceleration due to gravity is 9.8 m/s, and his/her vertical velocity initially is 0.

Figure out how long the swimmer takes to travel 1.81 m at 3.6 m/s. That's also how long it takes to get from initial elevation to water level - you've now got t.

Then use the following formula:

x = x0 + v0t + .5at2

hurtingBrain

would you use thise equation to find t
V^2 = Vo^2 + 2at

hurtingBrain

opps.. i mean V^2 =Vo^2 + 2aX

hurtingBrain

nope scratch that the first one

physicsface

No, you just need to use v = d/t. Use your horizontal information to calculate time.

JoshMP

^ You need the final velocity to use that equation. Find the time to reach horizontal displacement, then use that time to find the vertical displacement.

hurtingBrain

so would the final velocity be 3.60 m/s

JoshMP

The horizontal velocity component would be 3.6 m/s, but the swimmer would also have a vertical velocity component due to gravitational acceleration. Use trig.

physicsface

JoshMP:

That's not needed for this problem. The swimmer travels a set horizontal distance at a set horizontal velocity; that can be used to find t.

hurtingBrain

how would i use trg if i only have one side and no degree

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