(L6) Mechanics 2 - Newton's Laws and circles

Question 1

What is tension?

Answer 1

Pulling force over a distance of a rope/chain which transmits force. Reaction force. a=F/m –> T=mg (N)

Question 2

What is torque?

Answer 2

A measure of a force that causes an object to rotate around an axis. (Nm)

Question 3

What is a force?

Answer 3

What causes an object to accelerate?

Question 4

Newton’s 1st law

Answer 4

An object continues at constant velocity unless an external forces acts on it.

Question 5

Netwon’s 2nd law

Answer 5

External force gives objects acceleration proportional to the force F=ma

Question 6

Newton’s 3rd law

Answer 6

Force’s come in symmetrical, opposite direction but equal in magnitude pairs.

Question 7

What direction does tension force act in? Towards or away from weight?

Answer 7

Away. It’s a pulling force only.

Question 8

How to solve for tension?

Answer 8

1. Force diagram
2. Choose direction to solve for
3. Solve use a=sum of F/m –>F=mg

Question 9

How does pushing on a door work? (Torqu)

Answer 9

Same amount of work is done regardless of if you push on handle or hinges. W=F*d.
Hinges: Larger force for smaller distance.
Handle: Smaller force for larger distance.

Question 10

What is a static torque?

Answer 10

Doesn’t produce angular acceleration.

e.g, bike at constant speed.

Question 11

What is a dynamic torque?

Answer 11

Change in angular acceleration,

e.g accelerating bike. change in drive shaft of accelerating car.

Question 12

What is a moment or moment of force?

Answer 12

Used interchangebly with torque.
The radius at which the force acts is sometimes called the moment arm.

Question 13

How is torque calculated?

Answer 13

0 is the angle between the force vector and the moment arm.

Question 14

When is the torque equation:

Answer 14

If force is at right angle to moment arm, sin becomes 1. It becomes negligible.

Question 15

How can direction of torque vector be found?

Answer 15

Right hand grip rule.

Fingers pointing in direction of force.
Torque vector points in direction of thumb.

Question 16

Why is diretion of torque vector important to know?

Answer 16

Counter clockwise or clockwise.

Plane in which object may be rotating.

Question 17

How to calculate weight force?

Answer 17

F,w=mg

Question 18

Forces are vectors, what does this mean?

Answer 18

They can have a magnitude and direction.

It also means there are components of a force, F.
Components mean that acting together, F,x and F,y have same effect as F.

Question 19

Time to fully go around circle

Answer 19

Period, T

Question 20

Distance to fully go around circle

Answer 20

2πr

Question 21

Velocity of around circle

Answer 21

v =2πr / T

Question 22

Assuming constant speed around circle, what is velocity like?

Answer 22

Magnitude of velocity is constant.
But direction of velocity is constantly changing, so velocity is changing.

Question 23

How to find change in velocity of a circle

Answer 23

Question 24

What is centripetal acceleration?

Answer 24

Acceleration towards the centre of a circle, which keeps velocity changing in direction as the object travels around it.

Question 25

What is centripetal acceleration’s equation?

Answer 25

Question 26

What is centripetal acceleration in terms of period?

Answer 26