[問題] 兩題物理 敬請大家指教
後學物理不好
很多觀念沒有完全弄懂
敬請大家多多指教
解釋越詳細越好
如果您認為答案有錯
也煩請不吝提出
謝謝
1.
A pole-vaulter vaults over the bar and falls onto thick padding. He lands with
a speed of 9.8 m/s ； the padding then brings him to stop in a time of 0.40s.
What is the average force on his body due to the padding during that time
interval? Express your answer as a fraction or multiple of his weight.
(題目大概是說 一位撐竿跳高運動員撐竿跳跳過竿子然後落到厚厚的墊子上 落地速度是
9.8m/s 墊子讓他在0.40s停止 請問在這段時間中墊子作用在運動員的平均力為何?)
A:3.5 times his weight
這題後學利用公式 F x △t = m x △v 算出的答案是F=24.5m
請問後學的觀念哪裡錯了
敬請大家指教
2.
Calculate the acceleration of a thin hollow cylindrical shell rolling down
a slope inclined at an angle θ to the horizontal.
(一個中空的球殼從角度θ的斜坡上滑下來 請問球的加速度為何?)
A:(gsinθ)/2
這題後學認為答案有錯 後學算的答案是(3gsinθ)/5
中空的球殼的轉動慣量為 2
I = ── x M x R^2 (M為球殼的質量 R為球殼的半徑)
3
敬請大家多多指教
解釋越詳細越好
謝謝
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