Force from car

Homework Statement

a car of mass 1500kg and decelerating 15ms-2. what is the total force of car on road from all tires?

W=mg
F=ma

The Attempt at a Solution

I'm not sure if the force is simply mg or if it is ma in this case. There is also a frictional force but I don't know if it applies here.
mg=15000?
ma=22500?

Redbelly98
Staff Emeritus
Homework Helper
Try drawing a free body diagram of the car. What are the forces that are present, and in what direction are they?

Also, in what direction (horizontal or vertical) does the car decelerate? Which force or forces are acting in that direction?

Try drawing a free body diagram of the car. What are the forces that are present, and in what direction are they?

Also, in what direction (horizontal or vertical) does the car decelerate? Which force or forces are acting in that direction?

well theres the weight of the car downwards, the normal force from ground probably equal to that since car isn't moving upwards. then in the horizontal there is each wheel friction in direction of car moving

Redbelly98
Staff Emeritus
Homework Helper
Yes: gravity downwards, normal force from ground upwards, and friction force horizontally. And two of those forces are exerted by the ground, so the car exerts equal-but-opposite forces on the ground.

Yes: gravity downwards, normal force from ground upwards, and friction force horizontally. And two of those forces are exerted by the ground, so the car exerts equal-but-opposite forces on the ground.

so would that be mg+ma because opposite of gravity would be mg and the force opposite friction seems to be ma or is there a separate y force and x force

a car of mass 1500kg and decelerating 15ms-2. what is the total force of car on road from all tires?

Difficult to tell. I expect this is not the answer the question is looking for, but it means you are in the process of having an accident so your tyres might not be generating any force at all!

I do not believe your tyres can generate 1.5g (I think the limit for road cars is around 1.1g with latest tech), unless you are in a race car with aerodynamic downforce, but then the car wouldn't weight more than 605kg. (due to Formula 1 construction rules 605kg or Formula 3 540kg.)

Redbelly98
Staff Emeritus