p1-p4

Independent variable

height of the ramp

Dependent variable

average speed of the marble down the ramp

Controlled variable

surface of the ramp

Apparatus

• Wooden ramp about 120 cm long

• Blocks of wood from about 5 cm high to about 15 cm high

• Metre stick – to measure height of block and distance on runway

• Pencil

• Stopwatch

• Marble

Method

1. Set up ramp against wooden block

2. Using ruler, draw two pencil lines in the ramp, one at top and other at the bottom

3. Measure the distance, x between these two lines (1m)

4. Measure the height of the ramp, h

5. Allow marble to roll down ramp, starting from rest at upper line and finishing at lower line

6. For each height h, time motion three times using stop watch and record the results in table

7. Calculate average time, t

8. Average speed is equal to x/t

Graph

• average speed (y axis)

• height, h (x axis)

• line of best fit is curve through origin of decreasing gradient

• shows average speed is not proportional to h, but increases non-linear

Results

as height of runway increases, average speed will also increase

Justification

• as height increases GPE of marble will also increase

• when moves down GPE is converted to kinetic energy

• a greater amount of kinetic energy at bottom will have greater speed

Error

main error is reaction time using the stop clock

Safety

• make sure the marble doesn’t fall on to the floor

• secure the runway with a clamp

• wear safety goggles

Independent variable

force applied to the free end of the spring

Dependent variable

extension of the spring

Controlled variable

spring constant

Apparatus

• Safety spectacles – one pair for each learner

• Helical spring

• Retort stand, boss-head and clamp

• G-clamp to clamp iron stand to bench

• Mass hanger and slotted masses up to about 500 grams

• Ruler

Method

1. Clamp retort stand with boss head and to bench

2. Attach helical spring and secure it

3. Measure natural length of spring with metre stick

4. Add 100g (1N) mass hanger

5. Measure extended length of the spring.

6. Calculate and record the extension

7. Add a second 100g mass

8. Repeat measurements and record results in a table

9. Plot graph of Force (load)/N) on the x-axis versus extension/cm on the y-axis

Graph

• force/N (y axis)

• extension/cm (x axis)

• line of best fit is straight line through origin up to point

• shows extension of spring is directly proportional to applied force up to limit of proportionality

• beyond it is not proportional and extension increases significantly

Results

as force applied increases, the extension of spring will also increase

Justification

greater stretching force has greater separation of atoms so increases length/ extension

Error

main error is reading stretched length of spring, keep at eye level

Safety

• safety goggles must be worn

• stretched spring could fly off

• retort stand must be secured to bench to prevent it falling

Independent variable

forces applied to suspended metre rule

Dependent variable

distances from attached masses to pivot

Controlled variable

Apparatus

• Retort stand, boss-head and clamp

• G-clamp to clamp iron stand to bench

• 2 mass hangers and slotted masses up to 600 grams

• Uniform wooden metre rule

• Fine string

Method

1. Suspend and balance metre rule at 50 cm mark so it is in equilibrium

2. Using fine string, hang unequal masses, from either side of metre rule

3. Adjust position of masses until metre rule is balanced again

4. Record results in a table, and repeat for other loads/ distances

5. a force is trying to turn the metre stick anticlockwise/ clockwise

6. multiply force by distance to find their moments

Results

when metre rule is balanced the anticlockwise and clockwise moments are equal

Justification

principle of moments states, in equilibrium, total clockwise moment about a point equals total anticlockwise moment

Error

not balancing the metre rule correctly

Safety

• Clamp retort stand to the bench so it doesn’t fall

• Place an obstacle to prevent mass hangers falling on someone’s foot

• Safety glasses should be worn

Independent variable

vertical height of stairs

Dependent variable

time taken to run up stairs

Controlled variable

mass of the student

Apparatus

• Flight of stairs (or stepping platform)

• Bathroom/ newton scales to measure mass of a student

• Metre stick or ruler

• Stopwatch

Method

1. student uses bathroom scales to find mass in kilograms

2. mass is multiplied by 10 to find force in N

3. measure height of steps on staircase to determine average height

4. multiply number steps by average height to find vertical height h of the staircase

5. another student at the top uses a stopwatch to measure time taken to run up the stairs

6. experiment should be repeated to find an average

Results

divide work done (force x vertical height) by time taken

Justification

a heavier person requires more power to complete experiment in same time as a lighter person

Error

fewer stairs have shorter time and error in measured time increases to an unacceptable level

Safety

• running up stairs quickly makes it easy to fall

• only one person at a time to prevent collisions