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It seems obvious, but how do I explain it?

Explain how the total force opposing the motion of a car is affected when it is travelling up a hill. (1 mark)

I can appreciate the answer, I just can't write it down!

Any help would be much appreciated. :smile:

Reply 1

teachercol

There is an extra force opposing the motion which is the component of the car's weight down the slope = W sin (theta)

Reply 2

Theorist

teachercol

There is an extra force opposing the motion which is the component of the car's weight down the slope = W sin (theta)

But surely that remains constant as the car moves up the slope? After all the angle of the slope, the mass of the car and the value of g remain the same. :confused:

Reply 3

DoMakeSayThink

Sentooran

But surely that remains constant as the car moves up the slope? After all the angle of the slope, the mass of the car and the value of g remain the same. :confused:

Yes, it does. But the angle changes when you're on flat ground... If a car is going up an inclined plane of theta degrees to the horizontal, then the force opposing motion is constant.

Reply 4

Morbo

Sentooran

But surely that remains constant as the car moves up the slope? After all the angle of the slope, the mass of the car and the value of g remain the same. :confused:

Yeah, you're right - it is a constant force. This is the force that "opposes the motion".

Reply 5

Theorist

Thanks all.

But another question:

Why is it that the further you drive up a hill, the more work you need to do to move up it?

Reply 6

teachercol

Assuming the slope stays constant and you are going at a constant speed, the work done per unit time will stay constant.

The total work done will increase becasue you are gaining potential energy .