Space Time & Motion A.2 Forces & Momentum (id: 51295f0b7)

本题目来源于试卷: Space Time & Motion A.2 Forces & Momentum，类别为 IB物理学

[单选题]
An object of mass 1.0k p1jls3rkqv*:0 iv+ftg rests on a rough surface. Another object of mas,hebl, hhj,9y2wf qm: s 2.0kg is2myejl9,hhbhwq ,f,: connected to it with a string.

When the objects are released, the masses accelerate at $\frac{g}{2}$The work done by the tension of the string on the 1.0kg mass is 40J. Which of the following is correct for the 1.0kg mass during this period?
What is Magnitude of the force of friction /N and Distance travelled

A. 10;4.0m
B. 5;4.0m
C. 10;2.0m
D. 5;2.0m


参考答案:  B


本题详细解析:

$\underline{\text{Explanation}}$:

The acceleration is given as ${\displaystyle \frac{g}{2}}$ which is equal to ${\displaystyle \frac{10}{2}}=5m{s}^{-2}$

The free body diagram of the forces on the mass of $2.0kg$:

According to Newton's second law, the relationship between tension $T$, the weight of the object $W$ and the acceleration of the object:

$\begin{array}{rl}{\displaystyle F_{net}}& {\displaystyle =ma}\\ {\displaystyle }\\ {\displaystyle W-T}& {\displaystyle =(2.0)(5)}\\ {\displaystyle }\\ {\displaystyle (2)(10)-T}& {\displaystyle =(2.0)(5)}\\ {\displaystyle }\\ {\displaystyle T}& {\displaystyle =10N}\end{array}$

The free body diagram of the forces on the mass of $1.0kg$:

The reaction force $N$ of the ground on the box balances the weight $W$ of the object. According to Newton's second law, the relationship between Tension $T$, the force of friction on the object $F_f$ and the acceleration of the object

• $T-F_f=(1.0)(5)$

When the magnitude of $T$ is substituted in the equation;

• $10-F_f=(1.0)(5)$

• $F_f=5N$

The work done $W$ by $T$ can be found by the product of $T$ and the distance $d$ travelled by the object.

• $W=Td$

• $40=10d$
• $d=4.0m$

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