Internal forces acting within a system of particles can alter

Options

A. The linear momentum as well as the kinetic energy of the system
B. The linear momentum of the system, but not the kinetic energy of the system
C. The kinetic energy of the system, but not the linear momentum of the system
D. Neither linear momentum nor kinetic energy of the system

Answer

To solve the question regarding the effects of internal forces acting within a system of particles, we can break it down into the following steps:

### Step 1: Understand the Concept of Internal Forces
Internal forces are the forces that particles within a system exert on each other. These forces do not affect the overall motion of the system as a whole but can influence the motion of the individual particles.

**Hint:** Remember that internal forces are those that occur between objects within the same system.

### Step 2: Identify the Relevant Physical Quantities
The two main physical quantities we are interested in are:
- Linear momentum (p)
- Kinetic energy (KE)

Linear momentum is defined as the product of mass and velocity, while kinetic energy is defined as \( KE = \frac{1}{2}mv^2 \).

**Hint:** Recall the definitions of linear momentum and kinetic energy to understand how they are calculated.

### Step 3: Analyze the Effect of Internal Forces
When internal forces act on particles within a system, they can change the velocities of the individual particles. For example, if two charged particles attract each other due to electrostatic forces, they will accelerate towards one another, which increases their kinetic energy.

**Hint:** Consider how the motion of individual particles changes when they exert forces on each other.

### Step 4: Conservation of Linear Momentum
According to the law of conservation of momentum, the total linear momentum of a closed system remains constant if no external forces are acting on it. Since internal forces do not change the total momentum of the system, the linear momentum remains conserved.

**Hint:** Think about how momentum is conserved in a system with no external influences.

### Step 5: Change in Kinetic Energy
While the linear momentum of the system remains constant, the kinetic energy can change due to the work done by internal forces. As the particles move closer together, their speeds increase, leading to an increase in kinetic energy.

**Hint:** Remember that kinetic energy can change even if momentum is conserved.

### Conclusion
From the analysis, we conclude that internal forces can alter the kinetic energy of a system but do not affect the linear momentum. Therefore, the correct answer to the question is that internal forces can alter kinetic energy but not linear momentum.

**Final Answer:** Internal forces acting within a system of particles can alter kinetic energy but not linear momentum.