MECHANICS

Question 1

Scalar

Answer 1

a quantity with no direction and has magnitude

Question 2

Vector

Answer 2

a quantity with magnitude and direction

Question 3

name examples of scalars

Answer 3

• length/distance
• speed
• mass
• temperature
• time
• energy

Question 4

name examples of vectors

Answer 4

• displacement
• velocity
• force
• acceleration
• momentum

Question 5

Moment

Answer 5

the turning effect of a force around a turning point

Question 6

What does a moment of a force depend on

Answer 6

• size of the force
• how far the force is applied from the turning point

Question 7

equation for moments

Answer 7

moment (Nm) = force (N) * distance (m)

Question 8

what is the principle of moments

Answer 8

for a body to be in equilibrium, the sum of clockwise moments about any point equals the sum of the anticlockwise moments about the same point.

Question 9

couples

Answer 9

a pair of forces of equal size which act parallel to each other, but in opposite directions.

Question 10

centre of mass

Answer 10

the single point that you consider its whole length can act through (whatever its orientation).

• the object will balance around this point

Question 11

How to find the centre of mass by experiment

Answer 11

• Hang the object freely from a point
• Draw a vertical line downwards from the point of suspension - use a plumb bob to get your line exactly vertical
• Hang the object from a different point and draw another vertical line
• The centre of mass is where the two lines cross

Question 12

Speed

Answer 12

how fast something is moving regardless of direction

Question 13

displacement

Answer 13

how far an objects travelled from its starting point in a given direction

Question 14

velocity

Answer 14

the rate of change of an objects displacement (its speed in a given direction)

Question 15

acceleration

Answer 15

the rate of change of an objects velocity

Question 16

what does the gradient (curved) show in a displacement time graph

Answer 16

acceleration

Question 17

what does the gradient (straight line) show in a displacement time graph

Answer 17

velocity

Question 18

what does the gradient show in a displacement time graph

Answer 18

acceleration

Question 19

Drag forces

Answer 19

forces that oppose the motion of an object moving through a fluid (gas or liquid)

Question 20

Properties of drag forces

Answer 20

-Are always in the opposite direction to the motion of the object
-Never speed an object up or start them moving
-Slow down an object or keeps them moving at a constant speed
-Convert kinetic energy into heat and sound

Question 21

Lift

Answer 21

an upwards force on an object moving through a fluid. It is perpendicular to the fluid flow

Question 22

Describe the forces acting on a skydiver

Answer 22

-their velocity increases due to the downward force of their weight
-the increase in velocity means air resistance also increases and acceleration decreases
-eventually the skydiver reaches velocity where their weight equals the force of air resistance
-acceleration is 0 = terminal velocity

Question 23

Newton’s First Law

Answer 23

An object will remain at rest or move with constant velocity unless acted on by a resultant force

Question 24

Newton’s Second Law

Answer 24

The resultant force acting on an object with a constant mass is directly proportional to its acceleration

F = ma

Question 25

Newton’s Third Law

Answer 25

If Object A exerts a force on Object B, then Object B will exert a force on Object A which is equal in magnitude but opposite in direction

Question 26

A Newton’s third law force pair must be:

Answer 26

-The same type of force
-The same magnitude
-Opposite in direction
-Acting on different objects

Question 27

Linear momentum

Answer 27

the momentum of an object that is moving in only one dimension

Question 28

The Principle of Conservation of Momentum

Answer 28

The total momentum before a collision is equal to the total momentum after a collision, provided no external force acts