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CARA MENGHITUNG BERAT BESI BETON POLOS
Cara menghitung berat besi beton (polos):
Diameter x Diameter x Panjang x 0,006165
(diameter dalam satuan milimeter, panjang dalam satuan meter)
3,14 / 4 x 7854 / 1000000
3,14 adalah PI
4 (hitung volume tabung atau luas lingkaran) karena yang dikuadratkan diameter, maka dibagi 2 kuadart = 4
7854 adalah berat jenis baja (kg per meter kubik)
1000000 karena diameternya dalam milimeter ke meter kuadrat (1000 kuadrat)
Besi beton polos tidak bisa benar-benar bulat, karena proses rolling mill memang karakternya seperti itu. Besi (baja) bulat hasil dari mesin bubut saja, ada toleransinya, apalagi hasil penggilingan. Untuk itu, biasanya, untuk mendapatkan diameter besi beton, diukur beberapa kali, dan hasilnya dirata-rata.
Cara menghitung besi beton polos tersebut tidak berlaku untuk menghitung berat besi ulir (sirip). Diameter dalam besi beton ulir tidak bisa biasanya tidak persis sama untuk hasil pada ukuran tertentu, karena tebal dan kedalaman ulirnya tidak sama, tergantung pembuatan matrasnya (calibernya).
Untuk menghitung berat besi kotak (nako / virkan):
Diameter x Diameter x Panjang x 0,007854
Angka (nilai) 0,007854 adalah berat jenis baja (kg per meter kubik) dibagi 1000000 karena diameternya dalam milimeter ke meter kuadrat (1000 kuadrat)
Negative View of U.S. Race Relations Grows, Poll Finds
Public perceptions of race relations in America have grown substantially more negative in the aftermath of the death of a young black man who was injured while in police custody in Baltimore and the subsequent unrest, far eclipsing the sentiment recorded in the wake of turmoil in Ferguson, Mo., last summer.
The poll findings highlight the challenges for local leaders and police officials in trying to maintain order while sustaining faith in the criminal justice system in a racially polarized nation.
Sixty-one percent of Americans now say race relations in this country are generally bad. That figure is up sharply from 44 percent after the fatal police shooting of Michael Brown and the unrest that followed in Ferguson in August, and 43 percent in December. In a CBS News poll just two months ago, 38 percent said race relations were generally bad. Current views are by far the worst of Barack Obama’s presidency.
The negative sentiment is echoed by broad majorities of blacks and whites alike, a stark change from earlier this year, when 58 percent of blacks thought race relations were bad, but just 35 percent of whites agreed. In August, 48 percent of blacks and 41 percent of whites said they felt that way.
Looking ahead, 44 percent of Americans think race relations are worsening, up from 36 percent in December. Forty-one percent of blacks and 46 percent of whites think so. Pessimism among whites has increased 10 points since December.
The poll finds that profound racial divisions in views of how the police use deadly force remain. Blacks are more than twice as likely to say police in most communities are more apt to use deadly force against a black person — 79 percent of blacks say so compared with 37 percent of whites. A slim majority of whites say race is not a factor in a police officer’s decision to use deadly force.
Overall, 44 percent of Americans say deadly force is more likely to be used against a black person, up from 37 percent in August and 40 percent in December.
Blacks also remain far more likely than whites to say they feel mostly anxious about the police in their community. Forty-two percent say so, while 51 percent feel mostly safe. Among whites, 8 in 10 feel mostly safe.
One proposal to address the matter — having on-duty police officers wear body cameras — receives overwhelming support. More than 9 in 10 whites and blacks alike favor it.
Asked specifically about the situation in Baltimore, most Americans expressed at least some confidence that the investigation by local authorities would be conducted fairly. But while nearly two-thirds of whites think so, fewer than half of blacks agree. Still, more blacks are confident now than were in August regarding the investigation in Ferguson. On Friday, six members of the police force involved in the arrest of Mr. Gray were charged with serious offenses, including manslaughter. The poll was conducted Thursday through Sunday; results from before charges were announced are similar to those from after.
Reaction to the recent turmoil in Baltimore, however, is similar among blacks and whites. Most Americans, 61 percent, say the unrest after Mr. Gray’s death was not justified. That includes 64 percent of whites and 57 percent of blacks.
The nationwide poll was conducted from April 30 to May 3 on landlines and cellphones with 1,027 adults, including 793 whites and 128 blacks. The margin of sampling error is plus or minus three percentage points for all adults, four percentage points for whites and nine percentage points for blacks. See the full poll here.