# Calculating Net force

1. Oct 11, 2012

### socialfox

1. The problem statement, all variables and given/known data
Dough boy took a ride in his new car, he hammers the throttle in 2 seconds and his velocity is 45 km/hr (assume constant acceleration). The mass of the Viper is approximately 800kg, Find the net force acting on the viper.

To be honest I am clueless on this question, I have done it myself and gotten the wrong answers. The answer to the net force is 5000N as stated in the answers part but I am not sure how to get that. Would appreciate any help.

2. Oct 11, 2012

### howie8594

First, find the acceleration using a kinematics equation, and then use Newton's second law to find the net force.

3. Oct 11, 2012

### socialfox

Hi there can you please provide the kinematic equation? Is it a=v/t ? If so I got 22.5 m/s2 which I suspect is wrong...

4. Oct 11, 2012

### howie8594

Acceleration is not v/t. Remember that acceleration is a change in velocity, so you can't just write v/t because you've got all sorts of values you could plug in for velocity. You're half right though. Try the change in velocity over the time, or Δv/t.

Also, it's not stated in this problem, but I think you should assume the car's initial velocity is 0 m/s.

5. Oct 11, 2012

### socialfox

Okay I just got the answer, thanks for reminding me of the kinematic equations. I was focused on solving this with only dynamic equations.