It's about one-and-one-tenth times as heavy as a Golf Ball
In other words, 50 grams is 1.09 times the weight of a Golf Ball, and the weight of a Golf Ball is 0.9183 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 45.93 g. 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 nine-tenths as heavy as a Tennis Ball
In other words, 50 grams is 0.867 times the weight of a Tennis Ball, and the weight of a Tennis Ball is 1.15 times that amount.(ITF Standard; for Type 2 ball)
Per International Tennis Federation standard, regulation tennis balls must weigh about 56.0 g to 59.4 g. 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 three-fourths as heavy as a Battery (C)
In other words, 50 grams is 0.77 times the weight of a Battery (C), and the weight of a Battery (C) is 1.3 times that amount.(Alkaline)
A "C" size battery weighs 65 g. C batteries are typically used in medium-drain devices such as musical instruments.
It's about one-and-a-half times as heavy as a Light Bulb
In other words, 50 grams is 1.5 times the weight of a Light Bulb, and the weight of a Light Bulb is 0.67 times that amount.(a.k.a. lamp) (for A19-size, 60w, incandescent bulb by Bulbrite; package weight)
A standard, sixty-watt light bulb weighs about 34 grams. The tightly-coiled filament inside a bulb of this size would measure about 579mm if uncoiled and stretched out.
It's about half as heavy as a Deck of Cards
In other words, 50 grams is 0.53 times the weight of a Deck of Cards, and the weight of a Deck of Cards is 1.9 times that amount.(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 94 g. 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 230,000 grams.
It's about two times as heavy as a Battery (AA)
In other words, 50 grams is 2.1 times the weight of a Battery (AA), and the weight of a Battery (AA) is 0.48 times that amount.(Alkaline)
An "AA" size battery weighs 24 g. AA batteries came into common use during World War II and were given their name by the American National Standards Institute (ANSI) Committee C18 because they were smaller than the "A" size batteries which were invented first.
It's about two-and-a-half times as heavy as a Mouse
In other words, 50 grams is 2.4 times the weight of a Mouse, and the weight of a Mouse is 0.42 times that amount.(a.k.a. "House mouse", Mus musculus) (adult)
The weight of a mouse is typically an average of 12 to 30 g. While most mice typically live two to three years, the Methuselah Mouse Prize — an award administered by a non-profit organization which advances aging-related research — was once awarded to a team of scientists whose research resulted in a mouse living just under five years.