It is easier to pull a lawn roller than to push it because pulling

Options

A. involves sliding friction
B. Involves dry friction
C. Increases the effective weight
D. Decreases normal reaction

Answer

To solve the problem of why it is easier to pull a lawn roller than to push it, we can analyze the forces acting on the roller in both scenarios.

### Step-by-Step Solution:

1. **Identify the Forces Acting on the Lawn Roller:**
- The weight of the lawn roller acts downward and is equal to \( mg \), where \( m \) is the mass of the roller and \( g \) is the acceleration due to gravity.
- There is a normal reaction force \( N \) acting upward from the ground.

2. **Consider the Case of Pushing the Lawn Roller:**
- When you push the lawn roller, you apply a force \( F \) in the horizontal direction.
- This pushing force adds to the weight of the roller, increasing the normal reaction force. Therefore, the normal reaction when pushing is given by:
\[ N_{\text{push}} = mg + F \]
- The frictional force \( f_{\text{push}} \) opposing the motion can be expressed as:
\[ f_{\text{push}} = \mu N_{\text{push}} = \mu (mg + F) \]
- Here, \( \mu \) is the coefficient of friction.

3. **Consider the Case of Pulling the Lawn Roller:**
- When you pull the lawn roller, you apply a force \( F \) in the horizontal direction, but this force acts at an angle, effectively reducing the normal force.
- The normal reaction when pulling is given by:
\[ N_{\text{pull}} = mg - F \]
- The frictional force \( f_{\text{pull}} \) opposing the motion can be expressed as:
\[ f_{\text{pull}} = \mu N_{\text{pull}} = \mu (mg - F) \]

4. **Compare the Frictional Forces:**
- From the expressions for frictional forces, we can see that:
\[ f_{\text{push}} = \mu (mg + F) \quad \text{and} \quad f_{\text{pull}} = \mu (mg - F) \]
- Since \( f_{\text{push}} \) includes an additional \( F \) compared to \( f_{\text{pull}} \), we can conclude that:
\[ f_{\text{pull}} < f_{\text{push}} \]
- This means that pulling the lawn roller results in less frictional force opposing the motion than pushing it.

5. **Conclusion:**
- Therefore, it is easier to pull a lawn roller than to push it because pulling decreases the normal reaction force, which in turn decreases the frictional force.

### Final Answer:
It is easier to pull a lawn roller than to push it because pulling decreases the normal reaction force, leading to a lower frictional force.

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