3. Dynamics

Question 1

F = ma is in here

Answer 1

okay

Question 2

Perhaps w=mg???

Answer 2

okay

Question 3

Annnd there’s tension here as well.

Answer 3

T = mg + ma???
suppose there’s negatives

Question 4

Wow there’s practically not much done in the booklet. It’s purely gonna be applied base for this one D:

Like i said, compare this to mechanics

Answer 4

But hey at least i can compare this to mechanics

It literally is mechanics

Question 5

Tell me about the different types of forces, how it’s produced and what it does?

Answer 5

Weight = mg - caused by gravity
Magnetic = magnets - ?
Upthrust = ? - opposes motion
Air resistance/drag = ? - ?
Electrostatic = ? - ?
Friction = rough surface - always opposes motion
Thrust/driving force = ? - ?
Tension = is it? - really?

Question 6

How to gain resultant net force?

Answer 6

1. Check which one is dominating
2. That minus the opposing forces
3. Voila

Question 7

Tell me the difference between mass and weight

Answer 7

Mass:
- Measure of matter in your body
- Measured in kg
- Is always the same

Weight:
- The force due to gravity
- Measured in newtons (N)
- Changes depends on the gravitational field of an object

Word equations:
Weight (N) = mass (kg) x acceleration (ms^-2)
W = mg

Question 8

Define Newton?

Answer 8

A resultant force of 1 newton is produced when a mass of 1kg accelerates at 1ms^-2

Question 9

What is Newton’s 1^st law?

Answer 9

An object remains at state or at constant speed unless acted upon an external force

Question 10

What is Newton’s 2^nd law?

Answer 10

F = ma = m([v-u]/2) = (mv - mu)/t

• Acceleration of an object is directly proportional to the size of the resultant force acting
• Acceleration ^ = resultant force ^
• Therefore in graph = straight line
• Think deep about what u get from gradients too (mass)

Rate of change of momentum of an object is proportional to the resultant force acting on it, and takes place in the direction of the force

Question 11

What is Newton’s 3^rd law?

Answer 11

If you apply a push force on a wall, then the wall will push back with an equal and opposite force on you

Example:
Describe what happens to the two trolley cars when the spring is released?
- Trolley A exerts a force on trolley B
- Trolley B exerts an equal and opposite force on trolley B
- Both separating in opposite directions

Question 12

What is linear momentum?

Answer 12

The product of its mass and its velocity
(p = mv)

Question 13

Tell me about the principle of conservation of momentum?

Answer 13

Momentum is always conserved during a collision

In any collision within an isolated system, the total momentum of the interacting bodies remains constant

(M1 x U1) + (M2 x U2 = (M1 x V1) + (M2 x V2)

Question 14

Equations/formulas needed to answer the questions?

Answer 14

Equations/formulas probably needed:
F - ma
W = mg
g = 9.81 ms^-2
a = (v-u)/t

Honestly, the answers to most of these be self explanatory, except when it comes to ….

Question 15

Tension:
A car of mass 1400kg is pulling a trailer of mass 600kg. It accelerates from rest to a speed of 9ms^-1 in a time of 60s on a level road. Assuming all resistance forces are negligible:
a) Calculate total force on engine required to produce this acceleration
b) Calculate the tension force in the tow bar

Answer 15

a) Calculate total force on engine required to produce this acceleration
- a = (v-u)/t = (9 - 0)/60 = 0.15ms²
- 1400 + 600 = 2000kg (total mass)
- f = ma = 2000 x 0.15 = 300N

b) Calculate the tension force in the tow bar
Car (mass 1400):
E - t = 1400 x 0.15
300 - 1400 x 0.15 = T
= 90N

Caravan (mass 600):
T = 600 x 0.15
= 90N

E - T = m x a
E = the total force to go forward type shi
S’pose know this equation in general

Question 16

Elevator:
A lift and its occupants have a total mass of 1200kg
Calculate tension in lift cable when lift is:
a) Stationary
b) Going up at a constant velocity of 5ms^-1
c) Going up at constant acceleration of 0.4ms^-2
d) Going down at constant deceleration of 0.4^-2

Answer 16

a) Stationary
- Up = down
- T = 1200g

b) Going up at a constant velocity of 5ms^-1
- Constant ∴ just same as stationary
- Don’t get fooled from velocity given, it’s not acceleration

c) Going up at constant acceleration of 0.4ms⁰²
- F = ma
- But it’s actually -> T - mg = ma (unfortunately not given in data booklet)
- T - 1200g = 1200 x 0.4
- T = 1200 x 0.4 + 1200 x 9.81 = 12252N

d) Going down at constant deceleration of 0.4^-2
- F = ma
- But it’s actually -> mg - T = ma (still not given in data booklet)
- It’s -g cuz it’s decelerating downwards
- 1200g - T = 1200 x -0.4
- T = 1200 x 9,81 - 1200 x -0.4 = 12252N
(Well it’s the same as previous cuz, same acceleration n shi)

Question 17

Gun velocity???

Answer 17

Recoil velocity:
- Errr idk
- Collision = explosion
- Energy & momentum conserved cuz KE increases
- I can’t figure it out, make use of time I s’pose