Two masses are joined by a massless string. A \(30-\mathrm{N}\) force applied vertically to the upper mass gives the system a constant upward acceleration of \(3.2 \mathrm{m} / \mathrm{s}^{2} .\) If the string tension is \(18 \mathrm{N},\) what are the two masses?

Short Answer

Expert verified
The mass of the upper object is \( m_{1} = \frac{12N}{3.2 m/s^{2}} \) and the mass of the lower object is \( m_{2} = \frac{18N}{3.2 m/s^{2}} \).

Step by step solution

01

Identify the forces acting on each object

First, let's analyze the upper mass. It experiences two forces: the force applied (30N pointing upward), and the tension in the string (18N downwards). The net force can be calculated by subtracting the force of tension from the applied force. The lower mass only experiences one force, the tension of the string downwards.
02

Setup and calculate the mass of the upper object

Use Newton's Second law of motion (F=ma) to find the mass of the upper object. We know that net force on the upper object is the difference between the applied force and the tension which gives us 30N - 18N = 12N. The acceleration is given as 3.2 m/s^2. To find the mass, we rearrange the equation to m = F/a. So the mass of the upper object is \( m_{1} = \frac{F}{a} = \frac{12N}{3.2 m/s^{2}} \).
03

Setup and calculate the mass of the lower object

Similarly, for the lower mass, the force is the tension in the string which is 18N. The acceleration is the same as the upper mass, which is 3.2 m/s^2. Using the formula m=F/a, the mass of the lower object is \( m_{2} = \frac{F}{a} = \frac{18N}{3.2 m/s^{2}} \).

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