Vector/Freebody Diagrams And Resultant Force

Question 1

Is force a scalar or a vector? Give a definition for the type of quantity it is

Answer 1

Force is a vector meaning it has both magnitude and direction to it

Question 2

If an object is experiencing 0 resultant force, what could be happing to the object?

Answer 2

Either it remains stationary, or it will be moving at a constant speed (terminal velocity)

Question 3

What’s Newton’s 1st law?

Answer 3

Balanced forces- if something is moving, it will remain moving at that speed until it is stopped, if something is stationary, it will remain stationary until something moves it. Remains at constant speed.

Question 4

What is Newton’s 2nd law?

Answer 4

Resultant forces will make things accelerate. Force = mass * acceleration or F= ma

Question 5

What is Newton’s 3rd law? What makes it different from the others?

Answer 5

Every action has an equal and opposite reaction (this is the only law that acts on two objects – for example if I push on a table, the table pushes back on me. If the table overcomes the force though, it won’t move. If I don’t overcome the force, I will move backwards)

Question 6

Give me a definition for vector/freebody diagrams

Answer 6

Freebody diagrams are a simplified drawing of an object or a system. They show forces acting on the object or system.

Question 7

How are forces shown on a freebody diagram?

Answer 7

Forces are showing on arrows acting away from the centre of a box or a dot that represents the object.

Question 8

Why use arrows for freebody diagrams?

Answer 8

Because they can represent both the direction and the magnitude of a vector (force in this case)

Question 9

What does the size/length of an arrow show in a vector diagram?

Answer 9

Size and/or length represents the magnitude of the force. So the force’s strength.

Question 10

How is a force’s direction shown on a freebody diagram?

Answer 10

The direction force acts in is shown by the direction the arrow is pointing in.

Question 11

Should we label the arrows in vector diagrams? And if so with what?

Answer 11

In this particular case for forces, we should label the arrow with the names of the forces and the size of the forces in Newtons

Question 12

What is the definition of a component in forces?

Answer 12

One of the TWO forces that are at a right angle (so two forces should be at 90 degrees to each other). These two forces can be added together to form their all together resultant force. When we say added together. I mean in terms of Pythagoras so like a2 + b2 = c2, but c2 is the resultant force here.

Question 13

Any vector can be resolved into two components; explain this idea further

Answer 13

Well first of all, any vector can be resolved into two components at RIGHT ANGLES to each other. Second of all, it basically means that if a freebody diagram has a diagonal (north-east) arrow on it, it’s just the same as an arrow pointing upwards and an arrow pointing towards right

Question 14

In a freebody diagram, the object has an arrow on it, pointing upwards and an arrow on it, pointing to the left; how can this be simplified!

Answer 14

The upwards arrow and the left arrow can be simplified into a diagonal arrow that’s pointing to the north west of the object. You can find the force of that arrow using pythagoras

Question 15

Describe what a freebody diagram of an stationary object would look like? Wha forces are acting on it?

Answer 15

A stationary object freebody diagram looks like either a box or a circle in the centre with two arrows stemming from it. One points upwards and one points downwards. Both should be of same length. Either gravity or weight is the arrow pointing down and if the stationary object is on the ground (it has to be) then the upwards arrow is for reaction force

Question 16

What does a vector diagram of an object going at constant speed (terminal velocity) look like? What forces are acting upon it?

Answer 16

There should be a box or circle in the centre with four arrows stemming from the box/circle: all of the same size and length. The upwards arrow is reaction and the downwards arrow is either gravity or weight. The arrow to the right is thrust (if the object is going forward– to the right)
The arrow to the left is friction or air resistance

Question 17

If a ball was being pushed along the ground, what would that vector diagram look like? What forces are acting on it?

Answer 17

A box or a circle in the centre and four arrows stemming from it. Since it’s on the ground, there is an upwards arrow (reaction) and there downwards one is either weight or gravity. Both of those arrows are of the same length. Since the object is accelerating, the thrust arrow (lets say the right) is going to be longer than the friction/air resistance/drag arrow and maybe bigger

Question 18

If a ball was thrown straight up into the sky and is coming back down, what would it’s vector diagram look like. What forces would act on the ball.

Answer 18

If the ball is thrown straight up, only two arrows will be on the diagram. It’ll look like a box or a circle in the centre of the diagram and then a longer arrow pointing downwards and a much smaller one pointing upwards. The one pointing downwards is gravity or weight pulling the ball down and the small arrow upwards is air resistance, to combat the motion of falling

Question 19

a ball is thrown straight up and is falling back down. A student draws a vector diagram of this motion. He draws two arrows, a long arrow pointing down for gravity and a short arrow pointing up for air resistance. Why is the short arrow air resistance and not upthrust, lift or reaction? And why is it so small?

Answer 19

The arrow pointing upwards can’t be reaction because it’s not in contact with another surface so can’t be pushing BACK against something as a reaction. It can’t be upthrust because that’s only for keeping things afloat on liquid. It can’t be lift because that’s to keep things afloat on the air and that’s not what air resistance does. Air resistance combat and opposes the falling motion that the ball is making with gravity. It’s small because gravity has over come it, which is why the ball falls down

Question 20

What would the vector diagram look like for a ball that’s being rolled along the ground? Not being pushed, no one is touching it. Just rolling. What forces are interacting with the ball?

Answer 20

It would be a box or a circle in the centre of the diagram with three arrows stemming from it. There will be arrows pointing upwards and downwards. These are for forces reaction and weight/gravity. These arrows are the same length. There will be another smaller arrow pointing to the left (which for now is backwards). This is friction, and it is opposing the motion of the ball t forwards and rolling

Question 21

If a ball was rolled along the ground (nothing touching it except the ground) and someone drew a vector diagram on it, explain why there would be no arrow for thrust.

Answer 21

This is because the ball is no longer in contact with what provided it it’s initial force to get it moving. There is no source providing it a continuous push. It is still moving forwards and it will keep moving at the same pace unless something stops it or slows it down (frictional forces). So the reason there is no arrow is because yes the object is moving, but it’s moving because a force is acting upon it but because a force had acted on it and gave it the initial push.