# Help with F=ma

Each of the four wheels of a car pushes on the road with a force of 4.0 x 10³ N [down]. The driving force on the car is 8.0 x 10³ N [W]. The frictional resistance on the car is 6.0 x 10³ N [E]. Calculate the following:
(a) mass of the car
(b) net force on the car
(c) car's acceleration

For Fnet, would u also add 4(4.0 x 10³ N [up]) to the rest of vectors to cancel out the force all the tires have on the road? Or:
8.0 x 10³ N [W] + 6.0 x 10³ N [E]= 2.0 x 10³ N [W]

2.0 x 10³ N [W] + 4(4.0 x 10³ N [down])= Fnet
?!

I just did all that on my phone.. I'm desperate for some help :(

## Answers and Replies

rock.freak667
Homework Helper

Each of the four wheels of a car pushes on the road with a force of 4.0 x 10³ N [down]. The driving force on the car is 8.0 x 10³ N [W]. The frictional resistance on the car is 6.0 x 10³ N [E]. Calculate the following:
(a) mass of the car
(b) net force on the car
(c) car's acceleration

For Fnet, would u also add 4(4.0 x 10³ N [up]) to the rest of vectors to cancel out the force all the tires have on the road? Or:
8.0 x 10³ N [W] + 6.0 x 10³ N [E]= 2.0 x 10³ N [W]

2.0 x 10³ N [W] + 4(4.0 x 10³ N [down])= Fnet
?!

I just did all that on my phone.. I'm desperate for some help :(

I am led to believe that the entire mass of the car is supported by the wheels alone.

So yes the entire weight is 4(4x103) N, so the mass of the car is ?

I am led to believe that the entire mass of the car is supported by the wheels alone.

So yes the entire weight is 4(4x103) N, so the mass of the car is ?

m= 1.6 x 104 N

but what about Fnet

rock.freak667
Homework Helper

m= 1.6 x 104 N

but what about Fnet

There is a driving force and a resistance to the driving force, so what should be the net force between these two?

There is a driving force and a resistance to the driving force, so what should be the net force between these two?

so i don't have to worry about the force of the tires on the road?

Fnet=8.0 x 10³ N [W] + 6.0 x 10³ N [E]
Fnet= 2.0 x 10³ N [W]

rock.freak667
Homework Helper

so i don't have to worry about the force of the tires on the road?

Fnet=8.0 x 10³ N [W] - 6.0 x 10³ N [E]
Fnet= 2.0 x 10³ N [W]

you mean negative here

But yes that should be correct.