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.

**Not quite sure how to explain this! :(

Question

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. 

**Not quite sure how to explain this! :(

loser66 · Answer

think of friction force

ageta · Answer

he said explain.

loser66 · Answer

that is the hint.

anonymous · Answer

okay, friction force as in like the force when an object tries to move across a surface?

loser66 · Answer

That is the force appears between 2 objects, stops the moving. Like this, on the lean surface, the box doesn't drop because of this force.|dw:1416611922633:dw|

loser66 · Answer

|dw:1416611981733:dw|

anonymous · Answer

wait so if there is friction force, the box would stop moving?

loser66 · Answer

yup

anonymous · Answer

ooh okie yay!

loser66 · Answer

but to your problem, go backward, got me?

anonymous · Answer

how do i correlate that to newton's first law when explaining why the car engine must exert force between the car and the road to drive at a constant speed on a straight and level road? do i just use the friction force to explain?

and ohh what do you mean by backward? :/

loser66 · Answer

hey, is it not physics? why is it here?

loser66 · Answer

one more thing: our planet is not a flat one. hehehe

anonymous · Answer

yeah this is physics haha i haven't been able to "find more subjects" for awhile... not sure why... every time i try it, it pops up and then disappears! :(

anonymous · Answer

hehe okie:)

anonymous · Answer

oh would i say something like this to explain?

because of newtons 1st law, the car will remain at rest until an external force intervenes. When friction force comes in, the object will be able to move and then stay at a constant speed on a straight and level road.

is that right? not sure :/

loser66 · Answer

@agent0smith  please, say something, English is not my field

agent0smith · Answer

When a car is moving forward, both friction and air resistance act to slow it down, so the engine needs to provide an equal force to oppose those forces, so that the net force is zero, in order to keep the car at constant speed.

anonymous · Answer

so is that how you would explain it? what you wrote above? 

or do i say what i wrote above first (since the question says the car is at rest still?) and then add what you said for how it keeps moving?