# Physics of Motion

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1. Sep 13, 2015

### ElegantSir

1. The problem statement, all variables and given/known data
"Find the displacement for a 1971 Dodge challenger that achieves a velocity of 112km/h [west], accelerating at 2.7m/s^2 [west] for 3.2 seconds."

v2 = final velocity
d = displacement
a = acceleration
t = time

2. Relevant equations
The equation im given is this: d = v2t - 1/2at^2

3. The attempt at a solution
The answer I keep getting is approximately 85.4 but the homework is saying the answer is 113m [west].

This is how im getting 85.4: d = 31 * 3.2 - 1/2 * 2.7 * 3.2^2
d = 99.2 - 13.8
d = 85.4

Coincidentally if you add instead of subtract both numbers, you get the 113m the question is saying the answer is. Am I right to assume that the homework sheet is incorrect?

2. Sep 13, 2015

### Simon Bridge

The dodge starts at 112kmph ... from the description, would you say the car is speeding up or slowing down?

3. Sep 13, 2015

### ElegantSir

The car would be speeding up seeing as how their is a constant acceleration. So I would only assume you would end up faster than your starting speed

4. Sep 13, 2015

### Simon Bridge

If the car was just going at a constant speed ... how far would it have gone?
Since the car is accelerating, would it go farther or not so far?

Last edited: Sep 13, 2015