I kinematics can someone carefully check my work

In summary, three identical balls are thrown from the same height with the same initial speed. Ball a is thrown horizontally, ball b is thrown upward at some angle above the horizontal, and ball c is thrown at some angle below the horizontal. Disregarding air resistance, the motion of ball a will resemble an upside down parabola, while ball b will resemble a parabola going up then down, and ball c will resemble a downward parabola. When the balls reach the ground, ball c will have the fastest final velocity, followed by ball b, and then ball a. This is because ball c is thrown down with an initial speed and is accelerated by gravity, while ball b's velocity is counteracted by gravity until reaching
  • #1
squintyeyes
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three identical balls are thrown from the same height with the same initial speed...ball a is thrown horizontally, ball b is thrown upward at some angel above the horizontal and ball c is thrown at some angle below the horizontal...disregard air resistance and describe the motions of the three balls and compare the speeds of the balls when they reach the ground.


I think the aswer would go like this however i have reason to believe there is something wrong with this.

The motion of ball a will resemble an upside down parabola where zero starts at the maximum

pic 1

ball b will resemble a parabola as well but it will go up first then down. the reason being that the inital velocity will be counteracted by the acceleration of gravity downwards until the velocity is zero. when the velocity is zero that is the maximum and then the ball b will fall down to earth

pic 2

ball c will resemble the downward part of a parabola since it is only going down.

pic 3

in terms of final velocity it will be ball c being fastest, then ball b, then finally ball a being slowest.

the reason for ball c being the fastest is because you are throwing it down at an initial speed while it is being accelerated down at the acceleration of gravity.

the reason that ball b is faster than c is because at ball b's peak and ball c's peak they only have force of gravity in the y direction to speed the ball up. However, ball b is at a higher height so it will have a larger velocity when it hits the ground.
 

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  • #2
[tex]v^{2}=v^{2}_{0}+2ay[/tex]

What does that equation tell you about the velocity of b and c? Hint: c will not necessary hit the ground at a higher speed than b.
 
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  • #3
I am lost does that mean that ball b and c will hit the ground with the same velocity and why?
 
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  • #4
If they are launched at plus or minus the same angle with respect to horizontal. i.e. if the magnitude of the vertical component of their velocity is equal, they will land with the same speed.
 
  • #5
thanks
 

FAQ: I kinematics can someone carefully check my work

What is kinematics?

Kinematics is a branch of physics that deals with the motion of objects without considering the forces that cause the motion.

What are the basic concepts of kinematics?

The basic concepts of kinematics include displacement, velocity, acceleration, and time.

What is the purpose of carefully checking work in kinematics?

Carefully checking work in kinematics ensures accuracy and helps identify any mistakes that may have been made during calculations.

How do you check your work in kinematics?

To check your work in kinematics, you can use equations and formulas to calculate the values for displacement, velocity, and acceleration. Then compare these values to the original data to ensure they are consistent.

What are some common mistakes to watch out for when working with kinematics?

Common mistakes in kinematics include using incorrect units, misinterpreting data, and making calculation errors. It is important to double check all values and equations to avoid these mistakes.

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