# Homework Help: 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?
Is your answer faster or slower than the starting speed?

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