Mechanics

Question 1

Define scalar quantities

Answer 1

Has magnitude only.

Question 2

Define vector quantities

Answer 2

Has magnitude and direction.

Question 3

What are some examples of scalar quantities?

Answer 3

temperature
mass
distance
energy
speed
density
time

Question 4

What are some examples of vector quantities?

Answer 4

velocity
displacement
acceleration
force
weight
momentum

Question 5

How can you calculate the resultant vector?

Answer 5

pythagoras

Question 6

How can you calculate the final vector?

Answer 6

trigonometry

Question 7

What is instantaneous velocity?

Answer 7

Velocity at a given point

Question 8

Define speed

Answer 8

How fast something is moving (regardless of direction).

Question 9

Define displacement

Answer 9

How far an object has travelled from its starting point in a given direction.

Question 10

Define velocity

Answer 10

The rate of change of an object’s displacement.

Question 11

Define acceleration

Answer 11

The rate of change of an object’s velocity.

Question 12

What is meant by uniform?

Answer 12

Constant - e.g. uniform acceleration

Question 13

Define weight

Answer 13

The force on an object due to gravity.

Question 14

What is meant by free fall?

Answer 14

When the only force acting on the object is its weight, so it accelerates towards the ground.

Question 15

What shape does a displacement-time graph have?

Answer 15

Accelerating object: always be a curve.
Uniform acceleration: gradient is constant
Constant velocity: straight

Question 16

How do you find instantaneous velocity on a displacement-time graph?

Answer 16

Draw a tangent to the curve to a certain point and find its gradient.

Question 17

What does a v-t graph represent?

Answer 17

Acceleration

• straight line = uniform acceleration
• steeper gradient = greater acceleration

Question 18

What does the area under a v-t graph show?

Answer 18

Displacement of an object.

Question 19

What does a a-t graph show?

Answer 19

How an object’s acceleration changes over time.

Question 20

What are the features of a a-t graph?

Answer 20

height = object’s acceleration at that time
area under graph = object’s change in velocity
if a is 0 = constant velocity

Question 21

What is Newton’s first law?

Answer 21

An object at rest stays at rest and an object in motion stay in motion unless acted upon by unbalanced forces.

Question 22

What is Newton’s second law?

Answer 22

Acceleration is directly proportional to the magnitude of the net force and inversely proportional to the mass of the object. F = ma

Question 23

What is Newton’s third law?

Answer 23

For every action, there is an equal and opposite reaction.

Question 24

State the properties of pairs of forces in an interaction between bodies

Answer 24

• act in opposite directions
• equal magnitude
• same type of force
• act on same bodies

Question 25

What is the principle of conservation of linear momentum?

Answer 25

Momentum is always conserved (when no external forces act).

Question 26

Define the ‘moment of a force’

Answer 26

The turning effect of a force

Question 27

What is the principle of conservation of energy?

Answer 27

Energy cannot be created or destroyed, only transferred to one store or another.

Question 28

What are the two main types of friction?

Answer 28

Friction between:

• solids
• fluids (drag/air resistance)

Question 29

What is terminal velocity?

Answer 29

When the friction force equals the driving force.

Question 30

How does weight and air resistance act on a skydiver?

Answer 30

• leaves plane: accelerates (freefall)
• air resistance = weight (terminal velocity)
• after parachute: air resistance increases (bigger than their weight)
• slows down until new terminal velocity reached again