A block of mass 1 kg is placed on a horizontal surface . The reaction force to the weight of the block is

Options

A. The 10 N normal force from the surface
B. The 10 N reaction force from the block of the surface
C. The weight of the earth
D. A 10 N force on earth

Answer

To solve the problem, we need to determine the reaction force to the weight of a block that is placed on a horizontal surface. Here’s the step-by-step solution:

### Step 1: Identify the weight of the block
The weight of the block can be calculated using the formula:
\[ \text{Weight} (W) = \text{mass} (m) \times \text{acceleration due to gravity} (g) \]
Given:
- Mass of the block, \( m = 1 \, \text{kg} \)
- Acceleration due to gravity, \( g \approx 10 \, \text{m/s}^2 \)

Calculating the weight:
\[ W = 1 \, \text{kg} \times 10 \, \text{m/s}^2 = 10 \, \text{N} \]

### Step 2: Understand the forces acting on the block
When the block is placed on the horizontal surface, it exerts a downward force equal to its weight (10 N) on the surface due to gravity.

### Step 3: Apply Newton's Third Law
According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. Therefore, the surface will exert an upward force on the block, which is called the normal force.

### Step 4: Determine the normal force
Since the block is in equilibrium (not accelerating), the normal force exerted by the surface must balance the weight of the block. Thus, the normal force (reaction force) will also be:
\[ \text{Normal Force} = 10 \, \text{N} \]

### Conclusion
The reaction force to the weight of the block is equal to the normal force, which is:
\[ \text{Reaction Force} = 10 \, \text{N} \]

### Final Answer
The reaction force to the weight of the block is **10 N**.

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