It's about 550 times as heavy as a Deck of Cards
In other words, the weight of a Deck of Cards is 0.0019 times 50 kilograms.(ISO 216 B8 size, a.k.a. "poker size" 63 x 88 mm, 52-card deck)
A deck of 52 ISO 216 B8-size playing cards weighs 0.094 kilograms. Utilizing nearly 3,700 decks, the record-holding largest card tower was built in early 2010, stood over 3.5 m (11 ft), and weighed over 272 kg.
It's about 750 times as heavy as a Battery (C)
In other words, the weight of a Battery (C) is 0.0013 times 50 kilograms.(Alkaline)
A "C" size battery weighs 0.065 kilograms. C batteries are typically used in medium-drain devices such as musical instruments.
It's about 850 times as heavy as a Tennis Ball
In other words, 50 kilograms is 867 times the weight of a Tennis Ball, and the weight of a Tennis Ball is 0.00115 times that amount.(ITF Standard; for Type 2 ball)
Per International Tennis Federation standard, regulation tennis balls must weigh about 0.0577 kilograms. Competition balls are also tested for bounce height, with the standards requiring that a ball dropped from 254 cm must bounce back to a height of 135 cm to 147 cm.
It's about 1,000 times as heavy as a Golf Ball
In other words, 50 kilograms is 1,089 times the weight of a Golf Ball, and the weight of a Golf Ball is 0.0009183 times that amount.(per R&A USGA Rules of Golf; maximum rule weight)
According to the Rules of Golf (as approved by the United States Golf Association and the Rules Committee of the Royal and Ancient Golf Club of Saint Andrews), golf balls must weigh no more than 0.04593 kilograms. Golf balls are not required to have the familiar dimpled pattern, but the design has been popular since its invention in 1905 because it reduces drag while increasing lift.
It's about one-one-thousand-five-hundredth as heavy as The Space Shuttle
In other words, the weight of The Space Shuttle is 1,400 times 50 kilograms.(for Endeavour, a.k.a. OV-105, a.k.a. Orbiter Vehicle-105) (empty weight, excluding main engines)
When empty, the space shuttle Endeavour weighs 71,000 kilograms. The shuttle's spacious cargo bay carried the Chandra X-ray Observatory into orbit in 1999 — a payload that weighed 19,737 kg.
It's about 1,500 times as heavy as a Light Bulb
In other words, the weight of a Light Bulb is 0.00067 times 50 kilograms.(a.k.a. lamp) (for A19-size, 60w, incandescent bulb by Bulbrite; package weight)
A standard, sixty-watt light bulb weighs about 0.034 kilograms. The tightly-coiled filament inside a bulb of this size would measure about 579mm if uncoiled and stretched out.
It's about one-two-thousandth as heavy as a Blue Whale
In other words, 50 kilograms is 0.000478 times the weight of a Blue Whale, and the weight of a Blue Whale is 2,090 times that amount.(Balaenoptera musculus)
Blue whales weigh between 73,000 and 136,000 kg. The largest mammal to have ever lived, blue whales feed almost exclusively on krill — tiny invertebrates weighing about 0.001 kilograms each.