Materials

Question 1

What factors to look for in material graphs when comparing materials

Answer 1

Young modulus (stiffness)
Breaking stress
Elastic behaviour
Plastic deformation
Hookes law

Question 2

Investigating extension

Answer 2

1. Measure original length of the spring
2. Add masses to spring and measure change in length each time and calculate the extension
3. Plot graph of force against extension, gradient is stiffness

Question 3

Breaking stress and ultimate tensile strength

Answer 3

Stretch at which a material breaks
Maximum stress the material can withstand

Question 4

Determine the young modulus of a material

Answer 4

Reduce percentage uncertainty- long thin wire as this extends more for same force
Micrometer to find diameter of wire then calculate cross sectional area using average diameter
Add sun,alert weight till wire taught (this not included in measurements)
Measure distance between fixed end of wire and the marker ( unstretched length)
Add masses, recording the marker reading each time- extension is the difference between this and the unstretched length
Repeat until wire snaps
Plot stress strain graph
Young modulus is gradient

Question 5

Use a falling ball method to determine the viscosity of a liquid of known density

Answer 5

1. Elastic bands equal distances apart with first being at least halfway down cylinder
2. Record distance between each band
3. Micrometer to measure diameter of bearing
4. Drop ball into tube and start stopwatch when it reaches band 1 and record the times it reaches band 2 and 3
5. Repeat to get mean times
6. Calculate average velocity using the distance between bands and the average time
7. Calculate viscosity

Question 6

Pressure acting on an object due to a fluid

Answer 6

p=hpg
Depth times density times gravitational field strength

Question 7

Terminal velocity of a skydiver

Answer 7

Skydiver leaves plane and accelerates due to weight downwards until air resistance= weight
Once the forced are balanced they’re no longer accelerating and have reached terminal velocity, velocity is constant/ no resultant force w=u+d
Parachute opens causing increase in air resistance so there is now a resultant force upwards causing skydiver to accelerate at a decreasing rate until w=u again
Skydiver at a new but lower terminal velocity

Question 8

Terminal velocity of a vehicle

Answer 8

Car accelerates from rest using a constant driving force
Velocity increases and frictional forces increase which reduces the resultant force on the car, reducing the acceleration
Car reaches a velocity where frictional forces= driving force so car continues at a constant velocity

Question 9

Effect of increasing temperature on liquids

Answer 9

Less viscous
(Runnier)

Question 10

Yield point

Answer 10

Little force applied, large extension

Question 11

Elastic limit

Answer 11

Permanent deformation