题目
PHAS0009_24-25 1.3 Quiz 1 [0.25 hrs]
单项选择题
The gradient ∇ϕ \nabla\phi of the scalar field ϕ(r)=x2+2xy+x2z2 \phi(\mathbf{r}) = x^2+2xy+x^2 z^2 is equal to
选项
A.2(x+y+xz^2)\,\hat{\mathbf{e}}_x+2y\,\hat{\mathbf{e}}_y + 2x^2 z\, \hat{\mathbf{e}}_z
B.2(x+y+xz)\,\hat{\mathbf{e}}_x+2x\,\hat{\mathbf{e}}_y + 2x^2 z\, \hat{\mathbf{e}}_z
C.2(x+y+xz^2)\,\hat{\mathbf{e}}_x+2x\,\hat{\mathbf{e}}_y + 2x^2 z\, \hat{\mathbf{e}}_z
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标准答案
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思路分析
The problem asks for the gradient ∇φ of the scalar field φ(r) = x^2 + 2xy + x^2 z^2.
First, compute the partial derivatives with respect to each coordinate:
- ∂φ/∂x: Differentiate x^2 with respect to x to get 2x; differentiate 2xy with respect to x to get 2y; differentiate x^2 z^2 with respect to x to get 2x z^2. Summing these gives ∂φ/∂x = 2x + 2y + 2x z^2 = 2(x + y + x z^2).
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类似问题
Please select all the correct statements about the gradient.
Given the following function The gradient of f at (x,y) = (1,1) is
Tasks: Let's continue taking partial derivatives. Go to Example 11.3 and work through yourself how the three derivatives (with respect to 𝑥 , 𝑦 , and 𝑧 ) were computed. At the end of Example 11.3 we are also introduced to the definition of the gradient of a function. If 𝑓 is a function of 𝑛 variables and all the partial derivatives exist, then the gradient of 𝑓 is defined to be ∇ 𝑓 ( 𝑥 ) = ( ∂ 𝑓 ∂ 𝑥 1 ( 𝑥 ) , ∂ 𝑓 ∂ 𝑥 2 ( 𝑥 ) , … , ∂ 𝑓 ∂ 𝑥 𝑛 ( 𝑥 ) ) . This video goes over the definition and some facts on notation: Question: Which of the following functions have gradient ∇ 𝑓 = ( 𝑦 𝑒 𝑥 𝑦 + 𝑦 , 𝑥 𝑒 𝑥 𝑦 + 𝑥 ) ?
Given the following function f(x,y)=3x2+y2+1 The gradient of f at (x,y) = (1,1) is
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