Physics help please?

Question

Someone PLEASE help, I'm not here so people can do my homework but I'm having trouble
A car accelerates southward due to a frictional force between the road and the tires.
a) In what directions the frictional force of the road on the tires? Why does that force exist?
* My answer is that the frictional force is opposite (north) of the tires. I say it exists because when 2 forces are pressed together closely it causes attraction between the two forces.
Am I right?
b) Is the frictional force static or kinetic? Explain your answer.
* I say that it's kinetic friction but I'm not sure why so please help.

7. In the kitchen, frcition sometimes helps and sometimes hinders.
a) Describe at leat two ways in which you can increase friction when you're trying to open a tight lid on a jar.
*** One way I say is pressing/pushing on the lid while opening and I can't think of another way.
b) What materials and methods can be used to decrease friction between food and a cooking surface?

Answer 1

You are correct about the direction of the frictional force, but it is because there must be a counterforce to the southward acceleration. Remember, for every action, there must be an equal and opposite reaction (one of Newton's laws).

b) It does not state if the car is accelerating from rest. If it is accelerating from rest, for a moment it is overcoming static friction, and for the balance of time, kinetic friction. If the car was already moving, it is all kinetic friction. Static friction takes more force, ie it takes more energy to accelerate from 0m/s to 1 m/s than it does to go from .1 m/s to 1.1 m/s

7 One way is to use a rubber holder, this increases to coeficient of friction to a higher amont than exist between the lid and your skin. Squeezing the lid more tightly as you turn increases the normal force on the lid increasing frictional forces. Heating the lid by running under hot water expands the metal faster than the glass, decreasing the Normal force between the lid and the jar and thereby decreasing the frictional force.

Some pans are coated with Teflon to make the surface more non stick, I prefer using a little melted butter or vegetable oil

Answer 2

For 7a, another way is to use a rubber potholder between your hand and the jar lid so that the rubber grips the lid and helps increase friction. For 7b, using wax paper under food undermines the friction, as do flour and cooking spray.