Acceleration math questions?

Question

1. if an object travels for 15 min with a constant velocity of 12 miles per hour west ,what is the acceleration?

2.A sportcar goes from a velocity of 12 meters per second east in 2 seconds. what is the cars acceleration?

3. A train takes a long time to stop. thats what makes trains so dangerous to people who cross the tracks when one is near. if a train is traveling at 30 miles per hour south and takes 12 minutes to come to a stop what is the trains acceleration?

I have most of the equation written out I just want to make sure I am getting it all down.

Answer 1

1. Constant velocity => acceleration is 0.

2. I assume this is "from a dead stop to a velocity of 12 m/s east". In this case a = (v-u)/t = 6 m/s^2 east. If it's going from 12 m/s east to a dead stop, the acceleration is -6 m/s^2 east or 6m/s^2 west.

3. The acceleration is (v-u)/t = 0.5/12 = 0.042 miles/min^2 = 0.019 m/s^2, north.

Answer 2

1) 0
2) -6 m/sec^2 east
You are forcing us to assume the car is coming to a stop.
It could be accelerating East with an undefined acceleration and to an undefined velocity.
3)-150 miles/hour^2 south

Answer 3

The acceleration is given by using dv/dx which as a effect is a(x) = a million/2*[(10x - x^2)^-a million/2] * {10 - 2x] whilst x = 4 it fairly is comparable to a(4) = a million/2*[(40- sixteen)^-a million/2]* [10-8] = a million/2 * [24^-a million/2]*2 = 24^-a million/2 = a million / ?24