It has both magnitude and direction
The "weight" is the name we give to the force of gravity on the object. They're the same thing.
Lets assume that s is the speed of the slower train and f is the speed of the faster train.
s = f - 16
f = 150 / t
s = 170 / ( t+2 )
-----------------------
170 / ( t+2 ) = 150 / t - 16 / t * ( t + 2 )
170 t = 150 * ( t + 2 ) - 16 t * ( t + 2 )
170 t = 150 t + 300 - 16 t² - 32 t
16 f² + 52 t - 300 = 0 / : 4 ( We will divide both sides of the equation by 4 )
4 t² + 13 t - 75 = 0
t 1/2 = ( -13 + √(169 + 1200 ) )/ 8
t = ( - 13 + 37 ) / 8 = 24 / 8 = 3
t = 3 h
s = 170 : ( 3 + 2 ) = 170 : 5 = 34 mph
Answer: The speed of the slower train is 34 mph.
A. A stretched catapult can do work when released so it must have potential energy.
b. A stone on the ground will not move on its own ever again so it has zero energy.
c. In order to roll an object there must be a friction force between the object and the ground (otherwise it will slide)
d. To lift a stone you must overcome the weight which is the force due to gravity.
e. Work and energy are both measured in Joules.
