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April 8th, 2018, 12:32 PM   #1
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Help Me Kin Assignment

I need help with question 3...I have no idea how to solve it..
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April 8th, 2018, 01:26 PM   #2
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projectile motion in 2 dimensions ...

(a) $\Delta y = v_0 \sin{\theta_0} \cdot t - \dfrac{1}{2}gt^2$

$\Delta y = -35 \, m$, $v_0 = 120 \, m/s$, $\theta_0 = 30^\circ$

solve the resulting quadratic for $t$

(b) using $t$ found in part (a) ...

$\Delta x = v_0 \cos{\theta_0} \cdot t$

(c) $v_{fx} = v_0 \cos{\theta_0}$ ... velocity in the $x$ direction remains constant

using $t$ found in part (a) ...

$v_{fy} = v_0 \sin{\theta_0} - gt$

$\theta_f = \arctan\left(\dfrac{v_{fy}}{v_{fx}}\right)$
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April 8th, 2018, 01:49 PM   #3
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3a) I got two answers as I used the quadratic formula, time cannot be negative so the answer I got is t=0.29s
b) I got 5.36m so I rounded off to 5.4m
c)-1.429 degrees = -1.43 degrees
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April 8th, 2018, 02:03 PM   #4
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seems your calculator is in radian mode ... change to degrees
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April 8th, 2018, 02:28 PM   #5
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OOpsss...thank u


3a)12.29s=12.3s
b)1278.25m=1278.3m
c)-0.58 degrees = -0.6 degrees

Last edited by mayak201; April 8th, 2018 at 02:30 PM.
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April 8th, 2018, 02:33 PM   #6
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$0 = 35 + 60t - 4.9t^2$

$a=-4.9$, $b=60$, $c = 35$

$\dfrac{-b - \sqrt{b^2-4ac}}{2a} \approx 12.8 \,sec$

(b) should be $\approx 1330 \, m$

(c) should be $\approx -32^\circ$
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