An object of unknown mass moves over 10 m alone the x direction under the effect

Question

An object of unknown mass moves over 10 m alone the x direction under the effect of a horizontally applied force of a magnitude of 200 N.

Consider the three following cases:

i)     the object starts from rest, in the absence of friction

ii)    the object starts from rest, in the presence of a constant force of friction of a magnitude of 185 N

iii)   the object starts from an initial velocity of 2 m/s, in the presence of a constant force of friction of magnitude of 200 N

For these three cases, if it takes 10 s for the object to undergo its motion, is it possible to determine the mass of the object? If so, what would be the object's mass?

Show your work and explain your reasoning.

Explanation / Answer

i) F = m a

since 10 s, x = 1/2 a t^2

10 = 0.5*a*10^2

a=0.2

F = m a

200 = m*0.2

m = 1000 kg

ii) once again will find that a = 0.2

200 -185 = m*0.2

m=75 kg

iii) No since 200-200 = 0

so no information about mass

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