P8

Question 1

Describe a scalar

Answer 1

a quantity with only magnitude (size) and no direction

Question 2

Examples of scalar quantities

Answer 2

• Distance
• Mass
• Time
• Speed
• Energy

Question 3

Examples of vector quantities

Answer 3

• Displacement
• Velocity
• Acceleration
• Weight
• Momentum
• Force

Question 4

What is a vector and how can they be represented

Answer 4

• A quantity with both magnitude and direction
• They can be represented by an arrow
• The length of the arrow is the magnitude
• The direction of the arrow is the direction of the vector

Question 5

Examples of non-contact forces

Answer 5

• Gravitational force
• Electrostatic force
• Magnetic force

Question 6

What is a force

Answer 6

A push or a pull that acts on an object due to the interaction with another object. It is a vector force.

Question 7

Examples of contact forces

Answer 7

• Tension
• Friction
• Air/water resistance
• Normal contact force

Question 8

Equation to calculate weight

Answer 8

W = mg
Weight = mass x gravitational field strength

units of weight are newtons

Question 9

What is the centre of mass

Answer 9

The point of an object at which its weight is considered to act

Question 10

Experiment to find the centre of mass of a piece of card

Answer 10

• Put a hole in the card and suspend it on a clamp stand rod
• Use a plumbline to draw the direction of the force
• Repeat with different points
• Where the lines meet is the centre of mass

Question 11

Equation for work done

Answer 11

• Worl=k done = force x distance
• W = Fs

Question 12

What is hookes law and the equation for it

Answer 12

The extension of a spring is directly proportional to the force applied giving the limit or proportionality is not exceeded

equation - Force = spring constant x extension (F = ke)

Question 13

How many forces are needed to stretch, compress or bend an object

Answer 13

• 2 for stretch and compress
• 3 for bend
• This means the forces are balanced
• If they weren’t, the elastic object would move instead

Question 14

Experiment for force on an spring

Answer 14

• Set up a clamp stand with a weight and a VERTICAL ruler and spring hanging with a horizontal splint
• This is the original length
• Add 1N weights in turn and record the length along the ruler
• Calculate extension by doing new length - original length
• Plot the results on a graph
• You will see that the extension is directly proportional to the weight (linear) and therefore elastic

Question 15

What is deformation and what are the two types

Answer 15

• Deformation is a change in the shape of an object. More than one force is applied so it changes shape instead of moving
• The two types are elastic and inelastic deformation

Question 16

What is the resultant force

Answer 16

A single force that has the same effect as all the original forces acting together

Question 17

What is a moment

Answer 17

The turning effect of a force around a pivot

Question 18

How are moments used in real life

Answer 18

• Wheelbarrows
• See-saws
• Crowbars
• Cranes

Question 19

Equation to find the moment

Answer 19

• Moment (Nm) = Force (N) x Distance (m)
• M = fd

Question 20

What can we say about the moments if an object is balanced

Answer 20

The sum of the anti-clockwise moments equals the sumn of the clockwise moments

Question 21

Why does an object topple over

Answer 21

• The line of action from the centre of mass (the weight) is outside the base
• There is an unbalanced (resultant) moment acting on the block
• The object then topples

Question 22

What do levers do to the turning effect of the force

Answer 22

• Transmit it to the other side of the pivot
• They are force multipliers so allow a froce to be applied further from the pivot

Question 23

Defenition of inelastic deformation

Answer 23

Where an object is stretched of compressed and it doesn’t go back to its original shape once the forces have been removed