Homework questions, hints please?

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The discussion revolves around solving physics homework problems involving projectile motion. One participant struggles to calculate the maximum height of a ball thrown upward with an initial speed of 10.4 m/s, using incorrect formulas and methods. Another question involves determining the initial vertical speed needed to reach a maximum height of 5.5 m, with confusion about initial velocity being zero. Participants emphasize the importance of showing calculations to identify errors, as misunderstandings in basic formulas lead to incorrect answers. The conversation highlights the need for clarity in applying physics equations and understanding the concepts of motion.
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Homework questions, hints please??!

1. A ball is thrown upward. Its initial vertical speed is 10.4 m/s, acceleration of gravity is 9.8 m/s^2, and maximum height hmax are shown in the figure below. What is its height, hmax? Answer in units of m. Neglect: air resistance

For this one I used 3 different formulas in different ways and each answer I got was wrong when I checked it. I divided 10.4 and 9.8 and got .9423076923 for time. Then I plugged that into a distance formula of d=ViT+1/2aT^2 and got 16.55510205 which was wrong.

2.A ball is thrown upward. Its initial vertical speed is v0, acceleration of gravity is 9.8 m/s^2, and maximum height is 5.5 m, as shown in the figure below. What is its initial vertical speed, v0? Answer in units of m/s. Neglect: Air resistance

So since the initial vertical speed is v0 wouldn't the initial velocity just be 0?? And so the answer is 0??
 
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Until you show how you got your incorrect answers, we'll hardly be able to help you. :rolleyes:
 
moshilover said:
1. A ball is thrown upward. Its initial vertical speed is 10.4 m/s, acceleration of gravity is 9.8 m/s^2, and maximum height hmax are shown in the figure below. What is its height, hmax? Answer in units of m. Neglect: air resistance

For this one I used 3 different formulas in different ways and each answer I got was wrong when I checked it...could someone give me a hint or show me how to do this??

Well, which equations did you use?

2.A ball is thrown upward. Its initial vertical speed is v0, acceleration of gravity is 9.8 m/s^2, and maximum height is 5.5 m, as shown in the figure below. What is its initial vertical speed, v0? Answer in units of m/s. Neglect: Air resistance

This one I got 10.38267788, but I checked this one too and says its incorrect. I used the distance formula...

Show your working, and it will be easier to see where you went wrong
 
... I divided 10.4 and 9.8 and got .9423076923 for time ...

My calculator gives another value for this calculation. You divided 9.8 by 10.4, which gives a value with a unit of per second.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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