Can someone help me with this physics problem?

Question

--->Amtrak's 20th century limited is en route from chicago to new york at 110 km/h when the engineer spots a cow on the track. The train brakes to a halt in 1.2 min, stopping just in front of the cow.

(a) what is the magnitude of the trains (constant) acceleration? (b) what is the direction of the acc?
(c) how far was the train from the cow when the engineer first applied the brakes

&

-->an objects is moving initially in the x direction at 4.5 m/s^2 when an acceleration is applied in the y direction for a period of 18 seconds. if the object moves equal distances in the x and y directions during this time, what is the magnitude of the acceleration?

Answer 1

The train went from 110 km/h to 0 in 1.2 min. The acceleration is velocity divided by time. 110 km/h = 110/60 km/min, to make all the units consistent. Therefore a = 110/60*1.2 = 1.53 km/min^2 = 0.425 m/sec^2

s = 0.5*a*t^2 = 1.1 km

x = 0.5*4.5*t^2
y = 0.5*a*t^2

x = y so 0.5*4.5*t^2 = 0.5*a*t^2

a = 4.5 m/sec^2

This is too obvious; if two accelerating objects move the same distance in the same time, the accelerations must be the same. Are you sure that the x direction motion is not a constant velocity of 4.5 m/sec?

if so, then

x = 4.5*t
y = 0.5*a*t^2

if x = y then 4.5*t = 0.5*a*t^2,

a = 2*4.5/t

for t = 18 sec, a = 0.5 m/sec^2