A toy dart gun generates a dart with 0.180 kg.m/s momentum and a velocity of 4.1 m/s. What is the mass of the dart in grams rounded to 2 significant figures?

1 Answer
Jan 27, 2017

Answer:

The mass of the toy dart is #"0.044 kg"# rounded to two significant figures.

Explanation:

Momentum is mass in motion. Momentum depends on the mass of the object in motion and its velocity. Because velocity is a vector quantity, momentum is a vector quantity, even though a direction was not included in this question.

The equation for momentum is #color(red)(rho=m*v)#, where #rho#, (pronounced "roe") is momentum, #m# is mass, and #v# is velocity.

Known
#rho=0.180color(white)(.)"kg"*"m/s"#

#v="4.1 m/s"#

Unknown
#m=???#

Solution
Rearrange the equation for momentum to isolate mass. Substitute the known values into the equation.

#color(red)(m=rho/v)#

#m=(0.180"kg"*cancel"m/s")/("4.1 "cancel"m/s")="0.044 kg"# rounded to two significant figures