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Figure 7 shows two of the forces acting on a uniform ladder resting against a vertical wall - AQA - A-Level Physics - Question 5 - 2017 - Paper 1
Question 5
Figure 7 shows two of the forces acting on a uniform ladder resting against a vertical wall. The ladder is at an angle of 60° to the ground. 1. Explain how Figure 7... show full transcript
Worked Solution & Example Answer:Figure 7 shows two of the forces acting on a uniform ladder resting against a vertical wall - AQA - A-Level Physics - Question 5 - 2017 - Paper 1
Step 1
Explain how Figure 7 shows that the friction between the ladder and the wall is negligible.
Answer
The figure suggests that the force exerted by the wall on the ladder is perpendicular to the wall. This indicates that there is no horizontal component of force acting along the wall, meaning that the frictional force is negligible.
Step 2
Draw an arrow on Figure 7 to show the direction of the resultant force from the ground acting on the ladder. Label your arrow G.
Answer
An arrow should be drawn vertically upward from the point of contact between the ladder and the ground to indicate the resultant force from the ground acting on the ladder. Label this arrow 'G'.
Step 3
Calculate the magnitude of the resultant force from the wall on the ladder.
Answer
Using the sum of clockwise moments equals the sum of anticlockwise moments, we can calculate the resultant force. The weight acts at the center of the ladder, which is at a distance of 4.0 m from the ground contact point. Thus, the moment due to the weight is:
390 imes 4.0 imes rac{1}{2}= 110 \text{ Nm}
Now considering the angle of the ladder, we have:
Solving this gives:
This results in:
Step 4
Suggest the changes to the forces acting on the ladder that occur when someone climbs the ladder.
Answer
When someone climbs the ladder, the vertical reaction force from the ground increases due to the additional weight of the person. The direction of the resultant force from the ground also changes as the distribution of forces is altered. The frictional force at the wall may also be affected; as the upward force increases, the component of weight from the wall would cause the ladder to push harder against the wall, increasing the friction element.