# Car crash project?

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1. Mar 29, 2015

### haveyouseenlyss

Okay so I have to do a project that examines whiplash and brain injury in physics. My scenario is a minivan full of 7 people of various masses. This van is at rest and gets struck from behind by a truck going 75 mph. What is a reasonable acceleration for the van after it gets struck? I'm trying to find the force applied on the car, so I can calculate the amount of g's each person is feeling and determine how susceptible they are to concussions (10-50 g's).

Also if anyone knows how I could incorporate angular kinematics, that'd be great.

2. Mar 29, 2015

### AlephNumbers

Are you familiar with momentum and impulse?

3. Mar 29, 2015

### haveyouseenlyss

Yes, I used momentum and impulse in my draft and was told to redo my project because it wasn't focused enough on the physics behind whiplash :(

4. Mar 29, 2015

### AlephNumbers

Okay. Think about the person in the car. If they are wearing a seatbelt, what happens when they get hit?

5. Mar 29, 2015

### haveyouseenlyss

Their body/head jolts forward and backward?

6. Mar 29, 2015

### AlephNumbers

Yes, but it is important to specify that their head and neck rotate due to the torque exerted at somewhere around the base of the neck by the seatbelt.

7. Mar 29, 2015

### AlephNumbers

If it were simply a linear motion then their heads would have to pop off their bodies and fly until they came into contact with something else. Surely you can see how absurd that would be?

8. Mar 29, 2015

### haveyouseenlyss

Yeah I get that, I'm just trying to figure out what a reasonable acceleration is for the car that gets hit

9. Mar 29, 2015

### AlephNumbers

Look up values for the mass of a truck and the mass of a minivan.