Forces and matter

Question 1

Why does stretching bending and compressing require more than one force?

Answer 1

• If there is only one force, the object will just move in the direction of the applied force
• If there is a force inwards from both sides, the spring will compress
• If there is an outwards force from both sides, the spring will stretch

Question 2

What is elastic distortion?

Answer 2

• When an object has been deformed, the object returns to its original shape after the load is returned. This is elastic distortion
• like an elastic band

Question 3

What is inelastic distortion

Answer 3

• When an object has been deformed, the object does not return to its original shape after the load is removed.
• like an elastic band which is past its elastic limit

Question 4

What is hooke’s law?

Answer 4

The extension of the string is directly proportional to the force applied
F = kx

Only works until elastic limit, after that it becomes inelastic.

Question 5

How to calculate energy required in stretching a spring?

Answer 5

E = 1/2 * k * x^2, area under graph

Question 6

spring practical method and some results

Answer 6

• Take a clamp to hold a spring
• Use another clamp to clamp a ruler
• Add first mass to spring
• Measure the extension and plot a point on the graph.
• Repeat for more masses until you have enough measurements
• large force large extension
• F = k * x
• Find work done by finding area under a graph.
• Up to the elastic energy

Question 7

What is atmospheric pressure? and how does it vary with height above the surface?

Answer 7

• total weight of air above a unit area at a certain altitude
• ATP decreases with height
• P = F/A
• Since the weight decreases as there is less particles above as you rise, the pressure decreases.

Question 8

pressure formula

Answer 8

p = f/a
force per unit area

Question 9

what is a fluid

Answer 9

gas and liquids

Question 10

how does a fluid exert force?

Answer 10

• fluid pressure exerts force at right angles to any surface in contact with the fluid

Question 11

What does pressure in a fluid depend on?

Answer 11

• pressure of fluid
• atmospheric pressure

Question 12

How does pressure in a fluid act on an object?

Answer 12

• Creates a force
• At a normal to the surface (right angles)
• All directions on object

Question 13

What is the pressure formula?

Answer 13

P = F/A

Question 14

Why does pressure in fluid vary with density and depth?

Answer 14

• Density: higher mass of liquid on object –> higher weight –> higher force
• depth: more weight above -> large force -> greater pressure

Question 15

pressure in a column of liquid formula

Answer 15

P = h× ρ × g

funny p symbol is density of water

Question 16

What is upthrust?

Answer 16

• When an object is either partially or completely submerged in a fluid, the pressure of the fluid exerts a force on it from every direction

Question 17

How does upthrust work?

Answer 17

• due to P = h x p x g, the bottom of an object has a higher pressure than the top in a fluid
• This means that the force acting on the bottom would be higher
• This creates a resultant force upwards, called upthrust.
• The force of the upthrust is equal to the weight of fluid which has been displaced by the object.
• If the upthrust is a lower force than the weight of the object, it will sink, otherwise it will float.
• Overall, if the object is denser than the liquid, it will float. Otherwise it will sink.