Mechanics

Question 1

Explaining displacement time graphs

Answer 1

• state and explain +/- displacement
• state and explain acceleration to resultant force
• state and explain velocity

Question 2

Explaining velocity time graphs

Answer 2

• state +/- velocity direction
• state what happens to velocity and explain due to resultant force
• state when velocity is 0
• explain motion chronologically
• constant acceleration as gravity is constant
• directional changes in velocity

Question 3

Explaining acceleration time graphs

Answer 3

• state if acceleration is/isn’t constant and why
• directional peaks in acceleration mean velocity is rapidly changing from - to +

Question 4

N1

Answer 4

If Fr = 0 then object is stationary or at constant v

Question 5

N2

Answer 5

Resultant force is equal to the mass of an object * the direction of the acceleration

Question 6

N3 `

Answer 6

When object a exerts a force on object b, object b exerts an equal and opposite force on object a

Question 7

N3 pairs criteria

Answer 7

• 2 objects
• same type of force
• opposite in direction
• equal in magnitude

Question 8

State N3 pairs on person on ground

Answer 8

1. pull from earth on person
2. pull from person on earth
3. push from person on ground
4. push from ground on person (R)

Question 9

Use N laws to explain rocket motion

Answer 9

1. rocket ejects gas backwards and applies a force on it
2. Due to N3 the gas applies an equal 7 opposite force back onto the rocket
3. rocket experiences a Fr, so by N2 the rocket accelerates forwards

Question 10

Define centre of gravity

Answer 10

The point where the entire weight of the object acts

Question 11

Define moment

Answer 11

F * perpendicular displacement between line of action of force and pivot

Question 12

Define moment principles

Answer 12

in a equilibric system sum of C.M = A.M