Why does the front end of a car “lift up” while accelerating?
In: Physics
When a car accelerates, the weight moves towards the back of the car. When braking, the opposite happens.
Because the wheels are moving faster than the car initially. The body of the car would be moving straight back, but the suspension only goes up and down.
Torque.
Rotational force transferred to the ground exceeds the weight of the front end of the vehicle, so it lifts in an equal reaction to the torque being applied.
I might be wrong, but I think I’m close.
If you want, you can think of this as an action-reaction thing. When Newton wrote that he was talking about forces, but it’s also true that every applied moment/torque produces an equal and opposite moment/torque.
Picture a car, facing to the right. (I was going to say pretend it’s a rear wheel drive, but this is a 2020 Mustang so we don’t have to pretend.)
https://www.fleet.ford.ca/is/image/content/dam/vdm_ford/live/en_ca/ford/nameplate/mustang/2020/collections/dm/20_frd_mst_rpro_gtp_twor.tif?croppathe=1_21x9&wid=1440
When it accelerates, the drivetrain applies a clockwise torque to the wheels. The reaction is that the wheels apply a counterclockwise torque to the drivetrain, and the car that’s attached to it.
For reasonable accelerations, the reaction torque is pretty mild and all it does is slightly reduce the downforce on the front wheels. But if your car is a beast, that torque can be enough to actually lift the front wheels off the ground.
The force from moving forward is applied at the tires right at the road surface. The car body can move independently of the axles a little because of the suspension. Force applied below, body of car with the majority of the weight above. Obviously the car body will move backwards when the tires move forward.
If it’s not obvious, consider a more exaggerated case where the contact with the ground where force is coming from and centre of mass are even further apart. If you were standing there on a rug and I pulled it forwards, your feet will come forwards with the rug. However, your heads going to go flying backwards. The car does the same thing, it just thankfully has a really low centre of gravity and a lot of weight so it doesn’t tip over. Motorcycles can exceed this though and flip if they accelerate enough.
The force that accelerates the car is taking place at the point where the driven tires are touching the road.
Every part of the car is above these contact points.
Inertia makes the rest of the car lag behind the contact points between the tires and the road. The suspension allows the body of the car to lag by tilting up.
The answer is wrong!
The tires in the back get the power. The front tires are just for turning (for now). Since the back tires get the power, if they suddenly accelerate they essentially push forward as the front stands still. So the front moves up and the back moves forward.
EDIT: I apologize, I assumed this is how it worked. This answer is wrong and you should not follow this.
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