A box residing on an inclined plane has following forces:
In the X- direction
Mg sin (theta) = horizontal component of weight of the box
f = Frictional force = uN , u = frictional factor, N= mg
In the Y- direction
upward force = Normal reaction of the box = mg
downward force = mg cos(theta) = vertical component of weight of the box
Answer:
Explanation:
work done=force * displacement
=500 N * 40 m
=2000 joule
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Use the conservation of angular momentum; angular momentum at the beginning = angular momentum at the end
Conservation of angular momentum:
I1 w1 = I2 w2
Where I is the moment of inertia. For a sphere, I=2/5 m R^2. Substituting into the equation above we get
w2 = I1 w1 / I2 = w1 m1 R1^2 / (m2 R2^2)
w2 = w1 4 * (R1/R2)^2
= 4*(1)*(7E5/7.5)^2
= 3.48E10 revs/(17days)
= 2.04705882 x 10^9 revs/sec
Answer:
The time the train blocked the crossway is
0.007934h=0.476 min=28.6 s
Explanation:
The average speed is given by
V= (Vi+Vf)/2
and
V= dx/dt
Where
Vi= initial speed
Vf= final speed
dx= change of position=0.384 km
dt=time the train blocked the crossway
dt=2dx/(Vi+Vf)
dt=2*0.384 km/(77.3 +19.5) km/h
dt=0.007934h
dt=0.007934h*(60min/1h)=0.476 min
dt=0.476 min*(60s/1min)=28.6 s
