Question

A boxcar of mass 200 tons at rest becomes uncoupled on a 10 degrees grade. If the track is considered to be frictionless, what speed does the boxcar have after 10 seconds?

A. 0.37 m/s

B. 0.59 m/s

C. 1.3 m/s

D. 4.3 m/s

Answer 1

Consider the given data. Mass of boxcar, m 200 tons Angle, e10° Time, t10s Acceleration due to gravity, g-9.8m/s' Draw the free body diagram of the system mgsin(10) 10° mgcos(10) 100 mg

Write the expression to calculate the acceleration from the free body diagram ma - mg sin (10) a g sin (10) Here, a is the acceleration Substitute the values in the above expression a 9.8xsin (10) Write the expression to calculate the final speed of boxcar using equation of motions V-u+at Here, v is the final speed of boxcar, u is the initial speed of boxcar and initially boxcar is at rest so u 0 Substitute the values in the above expression v 0+1.7x10 Therefore, the final velocity of the boxcar is 17 m/s Hence, none of the option is correct