7.4- FREE FALL

Question 1

What did Galileo Galilei discover about 4 centuries ago?

Answer 1

reasoned that as any number of identical objects must fall at same rate, then any one such object must fall at same rate as rest put together

concluded any two object must fall at same rate regardless of weights

Question 2

How did Galileo Galilei demonstrate the correctness of his theory?

Answer 2

releasing two different weights from the top of the Leaning Tower of Pisa

Question 3

What did Galileo want to know?

Answer 3

if a falling object speeds up as it falls

Question 4

What did not exist that Galileo needed?

Answer 4

clocks + stopwatches

Question 5

What was the simplest test that Galileo could think of to test if a falling object speeds up as it falls?

Answer 5

time a ball as it rolls down a plank

Question 6

What did Galileo devise for his experiment to test if a falling object speeds up as it falls?

Answer 6

dripping water clock, counting volume of drips as measure of time

Question 7

What did Galileo’s measurements for the experiment testing if a falling object speeds up as it falls show?

Answer 7

ball gained speed as it travels down slope

in other words, ball accelerated as it rolled down slope

Question 8

What did Galileo reason for his measurements on the experiment testing if a falling object speeds up as it falls?

Answer 8

acceleration would be greater the steeper the slop

Question 9

What did Galileo conclude from the experiment testing if a falling object speeds up as it falls?

Answer 9

object falling vertically accelerates

Question 10

What is one way of investigating the free fall of a ball?

Answer 10

make a multiflash photo/ video clip of ball’s flight as it falls after being released from rest

Question 11

What can be used to provide a scale when investigating the free fall of a ball?

Answer 11

a vertical metre rule

Question 12

What can be done to obtain a multiflash photo for investigating the free fall of a ball?

Answer 12

ordinary camera with a slow speed shutter may be used to record ball’s descent in a dark room illuminated by stroboscope

Question 13

What is a stroboscope?

Answer 13

flashing light

Question 14

What does the flashing light for investigating the free fall of a ball need to flash at?

Answer 14

a known constant rate of about 20 flashes per second

Question 15

What can be measured directly for the experiment investigating the free fall of a ball? (2)

Answer 15

time of descent of the ball

distance fallen by the ball from rest

Question 16

How can you work out if the acceleration is constant with the time of descent and distance fallen for the experiment investigating the free fall of a ball?

Answer 16

s = ut + 1/2at^2

u = 0 so :

s = 1/2at^2

Question 17

When comparing y = mx + c and s = 1/2at^2, if we let y represent s and x represent t^2, what would 1/2a and c be?

Answer 17

m = 1/2a

c = 0

Question 18

What should a graph of s against t^2 give?

Answer 18

straight line through the origin

Question 19

When the gradient of the line on a graph of s against t^2 is measured, what can be calculated?

Answer 19

acceleration

gradient (= 1/2a)

acceleration (= 2 * gradient)

Question 20

When no external forces are acting on an object apart from gravity, what is the value of acceleration known as?

Answer 20

acceleration of free fall

Question 21

What symbol is acceleration of free fall represented by?

Answer 21

g

Question 22

What is the value for the acceleration of free fall?

Answer 22

9.8 ms-2

Question 23

When measuring acceleration of free fall, what can be used to measure s and t?

Answer 23

electronic timer or motion sensor

Question 24

Should you repeat your measurements when measuring g and what to do with measurements?

Answer 24

yes to obtain average timing for each measured distance + plot suitable graph finding g