咁個令佢減速既力係幾多
更新1:
要成個calculatioin既過程
phy ~ mechanics
回答 (2)
2009-05-27 4:44 am
✔ 最佳答案
The solution will be simplier if momentum is used.Since impulse = change of momentum
i.e. force x time = final momentum - initial momentum
force x 5 = 500 x (0 - 15)
hence, force = - 500 x 15/5 N = -1500 N
The retarding force is equal to 1500 N
2009-05-27 3:56 pm
要使物件at rest，即它的末速度為零，v = 0
初速度，u = 15 ms-1
時間，t = 5 s
假設物件的減速度不變
用v = u + at
0 = 15 + a(5)
加速度，a = -3 ms-2
換句話說，即減速度為3 ms-2
再根據牛頓第二定律
F = ma
F = (500)(3)
所需的減速力，F = 1500 N
初速度，u = 15 ms-1
時間，t = 5 s
假設物件的減速度不變
用v = u + at
0 = 15 + a(5)
加速度，a = -3 ms-2
換句話說，即減速度為3 ms-2
再根據牛頓第二定律
F = ma
F = (500)(3)
所需的減速力，F = 1500 N
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