Answer to Question #97124 in Mechanics | Relativity for tsegay

Question #97124
A train travelling along a straight track starts from rest at point A and accelerates uniformly to 20m/s in 20s. It travels at this speed for 60s then slows down uniformly to rest in 40s at point C. it stays at rest at C for 30s, then reverses direction accelerating uniformly to 10m/s in 10s. It travels at this speed for 30s, then slows down uniformly to rest in 10s when it reaches point B.
a) Plot a graph of the motion of the train
b) Use your graph to calculate
i) The trains displacement from point A when it reaches point C
ii) The trains displacement from point A when it reaches point B
iii) The trains acceleration each time its speed changes
1
Expert's answer
2019-10-23T09:50:20-0400


Let's find the train's displacement from point A when it reaches point C. We should calculate the area of the trapeze ADEC:

S1=60+120220=1800S_1=\frac{60+120}{2}\cdot{}20=1800 m.

Now let's find the train's displacement from point A when it reaches point B. We should calculate the difference of areas of the trapeze ADEC and trapeze FGHB:

S2=S150+30210=1800400=1400S_2=S_1-\frac{50+30}{2}\cdot{}10=1800-400=1400 m.

Let's find the trains acceleration each time its speed changes.

0t20,0\eqslantless{}t\eqslantless{}20, a1=20020=1a_1=\frac{20-0}{20}=1 m/s2.

80t120,80\eqslantless{}t\eqslantless{}120, a2=02040=0.5a_2=\frac{0-20}{40}=-0.5 m/s2.

150t160,150\eqslantless{}t\eqslantless{}160, a3=10010=1a_3=\frac{-10-0}{10}=-1 m/s2.

190t200,190\eqslantless{}t\eqslantless{}200, a4=0(10)10=1a_4=\frac{0-(-10)}{10}=1 m/s2.


Need a fast expert's response?

Submit order

and get a quick answer at the best price

for any assignment or question with DETAILED EXPLANATIONS!

Comments

Pat
03.09.20, 20:45

Its absolutely right

Leave a comment