Dynamics 2

Question 1

What is Newton’s first law?

Answer 1

Every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it

Question 2

When are Forces Balanced?

Answer 2

If resultant force is zero

Question 3

What is Inertia?

Answer 3

The reluctance of the object to change it state of rest or motion, due to its mass

Question 4

What is Newton’s second law?

Answer 4

When a resultant force acts on an object of constant mass, the object will accelerate in the direction of the resultant force

Question 5

When are Forces Not balanced?

Answer 5

If resultant force is not zero

Question 6

Equation for resultant force

Answer 6

F=ma

Question 7

What is Newton’s third law?

Answer 7

If body A exerts a force on body B, body B will exert an equal and opposite force on body A

Question 8

Condition for Newton’s third law

Answer 8

The 2 forces occur as an action-reaction pair

Question 9

What is Friction?

Answer 9

Friction is a contact force that opposes or tends to oppose motion between surfaces in contact, due to irregularities on surfaces in contact

Question 10

Positive Effects of Friction

Answer 10

Enhances grip
Ensures that objects can slow down when needed

Question 11

How does Using Threads help to Enhance the Positive Effects of Friction?

Answer 11

To grip the road surface and roll without slipping

More grip to prevent skidding when it rains by channeling water out from under the tyres

Question 12

How does Using a Parachute help to Enhance the Positive Effects of Friction?

Answer 12

To increase air resistance

To fall slowly and land safely by increasing surface area

Question 13

How does Using Chalk help to Enhance the Positive Effects of Friction?

Answer 13

To absorb sweat and improve grip

Question 14

Negative Effects of Friction

Answer 14

Wear and tear occurs
Efficiency of some objects is reduced

Question 15

How does Using Wheels help to Reduce the Negative Effects of Friction?

Answer 15

Reduces friction due to circular shape
Smaller force can be applied to move objects around

Question 16

How does Using Ball Bearings help to Reduce the Negative Effects of Friction?

Answer 16

Reduces friction between moving parts due to spherical shape
Prevents moving parts from rubbing against each other

Question 17

How does Using Lubricants/Polished Surfaces help to Reduce the Negative Effects of Friction?

Answer 17

Adding a layer of lubricant between surfaces reduces friction
Polishing surfaces removes irregularities, reducing friction

Question 18

How does Using an Air Cushion help to Reduce the Negative Effects of Friction?

Answer 18

Friction between 2 surfaces reduced when thin layer of cushion between surfaces exists

Question 19

What happens when objects fall without Air Resistance?

Answer 19

Constant acceleration of 10m/s² downwards

Question 20

Characteristics of Air Resistance

Answer 20

Always opposes motion of moving objects
Increases with speed of object
Increases with surface area/size of object
Increases with density of air

Question 21

Objects falling with Air Resistance

Answer 21

Stage 1: After jumping, weight is a bigger force than air resistance, accelerates downwards
Stage 2: Air resistance increases until it is equal to weight, forces balanced and speed remains constant, known as terminal velocity
Stage 3: Parachute opened, air resistance increases dramatically, air resistance greater than weight, slows down
Stage 4: Air resistance reduces as object slows down until equal to weight, forces balanced and speed remains constant, new terminal velocity