Consider the falling and rolling motion of the ball in the following two resistance-free situations.
In one situation, the ball falls off the top of the platform to the floor. In the other situation, the ball rolls from the top of the platform along the staircase-like pathway to the floor. For each situation, indicate what types of forces are doing work upon the ball. Indicate whether the energy of the ball is conserved
and explain why. Finally, fill only 9 (nine) blanks for the 2kg ball.
Answers
Answer:
The only force doing work is gravity. Since it is an internal or conservative force, the total mechanical energy is conserved. Thus, the 100 J of original mechanical energy is present at each position. So the KE for A is 50 J.
The PE at the same stairstep is 50 J (C) and thus the KE is also 50 J (D).
The PE at zero height is 0 J (F and I). And so the kinetic energy at the bottom of the hill is 100 J (G and J).
Using the equation KE = 0.5*m*v2, the velocity can be determined to be 7.07 m/s for B and E and 10 m/s for H and K.
The answers given here for the speed values are presuming that all the kinetic energy of the ball is in the form of translational kinetic energy. In actuality, some of the kinetic energy would be in the form of rotational kinetic energy. Thus, the actual speed values would be slightly less than those indicated. (Rotational kinetic energy is not discussed here at The Physics Classroom Tutorial.)
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Given: Two resistance situation are given for falling and rolling motion of the ball.
Find: Fill the blanks.
Solution:
The only force doing work is gravity. Since it's an interior or conservative force, the full energy is preserved. Thus, the one hundred J of original energy is gift at every position. therefore the KE for A is fifty J.
The letter of the alphabet at a similar stairstep is fifty J (C) and so the KE is additionally fifty J (D).
The letter of the alphabet at zero height is zero J (F and I). and then the K.E. at very cheap of Capitol Hill is one hundred J (G and J).
Using the equation KE = zero.5*m*v2, the speed will be determined to be seven.07 m/s for B and E and ten m/s for H and K.
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