Frictional Forces And Resultant Force

Question 1

What is friction?

Answer 1

It’s the contact force of one surface rubbing or gripping on another surface

Question 2

True or false: friction will always act in the same direction as gravitational forces. Explain.

Answer 2

False: frictional forces always oppose motion forces.

Question 3

What will happen in an object has no forward force and only friction is acting on it?

Answer 3

Friction will cause the movement to stop and cause the object to stop too.

Question 4

Friction can be cause if one object produces movement but how else can it be caused? (hint: still to do with movement)

Answer 4

Friction is also caused when another force attempts to cause movement

Question 5

Give an example of another force attempting to cause movement

Answer 5

For example, pulling a box towards you. If you can pull it towards you, the force you’re exerting on the box is greater than the frictional forces. But if can’t move it, the frictional forces have prevented movement

Question 6

What will happen if acceleration forces equal frictional forces?

Answer 6

The object won’t move

Question 7

If friction is the only force acting on an object, what does that mean for the resultant force?

Answer 7

The resultant force will just be due to friction so the object will slow and stop in the end.

Question 8

If two forces acted on an object and one was friction, what does that mean for the resultant force? And what have you assumed?

Answer 8

The greater the frictional force, the smaller the resultant force because frictional will cancel out the opposite motion force and therefore reduced the net force and the acceleration. I’ve assumed the object is accelerating because it wouldn’t work any other way

Question 9

What does acceleration mean for the frictional force?

Answer 9

Acceleration means that a motion force is greater than a frictional force

Question 10

How is friction caused in terms of surfaces?

Answer 10

Friction is caused by roughness of surface.

Question 11

How is roughness of surface caused? Can there be a perfect smooth surface?

Answer 11

By irregularities. Irregularities mean that all surfaces aren’t smooth and are bumpy: even paper, they must have smaller microscopic ones.

Question 12

Explain how friction is caused by roughness of surface?

Answer 12

When two surfaces move against each other or when one surface moves across another, the irregularities will catch onto each other. With each ‘catch’ a small backwards force is created. The frictional force is the combined effect of the small forces.

Question 13

How would you increase friction? Explain

Answer 13

A greater surface area in contact with each other (more irregularities collide)
Objects that are pressed tighter against each other (irregularities will require a greater force to be moved past each other)

Question 14

How do we reduce friction then?

Answer 14

With a lubricant or having a smoother surface

Question 15

How do you reduce friction with a lubricant?

Answer 15

Lubricant is a substance is added between two surfaces to reduce friction. It keeps the objects’ surface slightly apart so irregularities will catch on less or not at all

Question 16

How do you reduce friction with smooth surfaces?

Answer 16

The smoother a surfaces, the smaller the irregularities so the lesser the friction

Question 17

List three examples of lubricants you can use for metals

Answer 17

Oil, grease and polish

Question 18

What are properties of a good lubricant?

Answer 18

– They should reduce the backwards/frictional force
– The would stay in place
– They should not cause rusting of metal if applied to it

Question 19

In real situations, objects have at least two forces acting on them along any direction. With this information, explain what resultant forces are

Answer 19

If you have a number of forces acting at a single point, you can replace them with a single force, so long as that force as the same effect as all the original forces: that singular force is called the resultant force

Question 20

How do you calculate the resultant force of an object?

Answer 20

If forces are going in the same line (parallel) the overall effect is found by adding those in the same direction and subtracting those in the opposite direction