You go shopping at Ikea and come home with the cabinet pictured. The specs sheet

Question

You go shopping at Ikea and come home with the cabinet pictured. The specs sheet says it has a height of 70 cm, a depth of 20 cm, a width of 70 cm and the (empty) mass is 13.20 kg. The load capacity of each shelf (including the bottom) is 5 kg. You wish to hang it on your wall, but you have only two screws and are worried that they might not be strong enough.

1. Where should you attach the screws to the cabinet? Why?

2. What will the force on the screws be when the cabinet is loaded to capacity?

3. If you are screwing into a wall made of 3/8 inch wallboard, and you are using a 1/8 inch diameter polly fasteners (see http://www.powers.com/pdfs/plastic/02105.pdf), will it hold? How do you know? If they will not hold, how are they most likely to fail?

Graded Assignment #12 Physics 50 The one about the Ikea cabinet Nornäs Class-door wall cabinet You go shopping at Ikea and come home with the cabinet pictured. The specs sheet says it has a height of 70 cm, a depth of 20 cm, a width of 70 cm and the (empty) mass is 13.20 kg. The load capacity of each shelf (including the bottom) is 5 kg. You wish to hang it on your wall but you have only two screws and are worried that they might not be strong enough 1. Where should you attach the screws to the cabinet? Why? 2. What will the force on the screws be when the cabinet is loaded to capacity? 3. If you are screwing into a wall made of 3/8 inch wallboard, and you are using a 1/8 inch diameter polly fasteners (see http://www.pouers.com/pdfs/plastic/02105

Explanation / Answer

(1)

We should attach the screws on upper corners so that they balance the torque due to cabinate weight and

torque due to reaction from the wall.

(2)

force on the screws F = Full load capacity / 2

there are 3 shelfs. so,

Full load capacity = 5*3 + 13.20 = 28.2 kg = 62.17 lb

so, F = 31.08 lb

(3)

Ultimate load capacity for polly with 3/8 inch wallboard and 1/8 inch is 80 lb tension and 120 lb shear.

Alllowable load capacity for polly fasteners is 20 lb tension and 120 lb shear.

Force on scrwes ( 31.08 lbs) is more than the allowable load capacity (30 lbs shear) but less than ultimate load

capacity (110 lbs shear).

Hence, they will hold but with less safety measures.

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