A 4-kg mass is connected to a 6-kg mass by a massless cord. A 120-N upward force is applied to the 4-kg mass, causing both masses to accelerate upward. The upward acceleration of the masses is
A) 12 m/s $2$
B) 2.2 m/s $2$
C) 9.8 m/s $2$
D) 5.8 m/s $2$

Question

Quizplus · Accepted Answer

The total force acting on the system is the 120-N upward force minus the gravitational force acting on both masses. The gravitational force is $F_g = (4\,kg + 6\,kg) \times 9.8\,m/s^2 = 98\,N$. The net force is then $120\,N - 98\,N = 22\,N$. The total mass is $4\,kg + 6\,kg = 10\,kg$. Using Newton's second law, $F = ma$, we find the acceleration $a = \frac{F}{m} = \frac{22\,N}{10\,kg} = 2.2\,m/s^2$.

A 4-Kg Mass Is Connected to a 6-Kg Mass by a Massless