2. According to Newton’s first law, if no force acts on an object, it will just continue moving. Explain in terms of Newton’s first law why a car engine must exert a force between the car and the road to drive at a constant speed on a straight and level road.

Question

2.	According to Newton’s first law, if no force acts on an object, it will just continue moving. Explain in terms of Newton’s first law why a car engine must exert a force between the car and the road to drive at a constant speed on a straight and level road.

anonymous · Answer

I think because of gravity

anonymous · Answer

well its all about physics.. and basic concepts ...

let me explain , i am good at it.. 

the first law states that, you no need to further push an object when it is free of obstacles.. so here in our car theory the obstacles...

1. friction by road,
2. friction by air...

what caused them both.. yes, the answer is gravity...
imagine... our earth without gravity.. 

car will float in space.. and air molecules no need to be so close to the earth surface.. and they will disperse over the wide space... finally, no friction.. we done,,,

ask me about gravity, i got my own theory... .
trust me i am Anti to Einstein's relativity...

anonymous · Answer

There are forces acting on the car and in the opposite direction of its motion.  The first is friction :$$F _{f}=\mu mg$$where Ff is the friction force; μ is the coefficient of friction; m is the mass of the car; and g is the acceleration of gravity.  The other major force working against the car is aerodynamic drag:$$F _{D}=\frac{ 1 }{ 2 }C _{D}A \rho v ^{2}$$where FD is the drag force; CD is the coefficient of drag; A is the aerodynamic area presented; ρ is the density of the air; and v is the speed of the car (technically the speed of air relative to the car's motion).  There are also forces present in the car that the motor has to overcome: friction in the motor;  driveline, and wheels.

anonymous · Answer

Bro.. U just nailed it..