Question

# 16. A shelf of uniform density is supported by two brackets at a distance of 1/8and % of the total length L from each end respectively. a) Find the ratio

of the reaction forces from the brackets on the shelf. Express your answer in the form of a decimal less than or equal to 1 to two significant figures. b) The rectangular shelf is now replaced with a uniform right-angled triangular shelf, as shown in the figure below. The centre of mass of a triangle lies at a point 1/3 of the perpendicular distance from the base to the tip. Find the new ratio of the forces on the two brackets. Express your answer in the form of a decimal less than 1 to two significant figures. c) The diagram 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. Explain how the diagram shows that the friction between the ladder and the wall is negligible. The ladder is 7.0m long and weighs 320N. Calculate the magnitude of the resultant force from the wall on the ladder. Suggest three changes to the forces acting on the ladder that occur when someone climbs the ladder.

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