Ask To Yourself

Question 1

What is accuracy?

Answer 1

Accuracy is a measure of how close a measured value is to the true (accepted value).

Question 2

What is random error? And what is the effect of random error?

Answer 2

Random error is chance difference between the observed and true values of something. An error that occurs due to unexpected changes during experiment. These can cause repeated results to differ from one another, effect the precision of the measurement.

Question 3

What is systematic error? And what is the effect?

Answer 3

Systematic error is consistent of proportional difference between the observed and true values of something. An error occurs due to faults in equipment or experimental method. These can cause the result to differ by the same amount of each time, making them predictable. They can occur due to not calibrating an instrument correctly.

Question 4

How to reduce the random errors?

Answer 4

1. Take at least three repeats and calculate a mean.
2. Use computers / data loggers.
3. Use higher resolution equipment.

Question 5

How can systematic error can be reduced?

Answer 5

1. Instrument should be recallibrated, or different instruments should be used.
2. Corrections or adjustments should be made to the technique.

Question 6

What is precision?

Answer 6

Precision is how consistent / close together repeat readings are. The closer they are the more precise they are.

Question 7

What is absolute uncertainty?

Answer 7

Uncertainty given as a fixed quantity. For example, 7 +- 0.6 V

Question 8

What is the percentage uncertainty in 17 +- 3 A?

Answer 8

3/17 x 100 = 17.647% ~ 18% (2 s.f)

Question 9

What is factorial uncertainty in 8 +- 0.5 m?

Answer 9

0.5/8 = 1.16

Question 10

How to reduce percentage and fractional uncertainty?

Answer 10

Measure larger quantities. For example, a longer rope will have a smaller percentage uncertainty that a shorter one.

Question 11

The time for 10 swings of a pendulum is 13 +- 0.3 s. What is the time and uncertainty for one swing?

Answer 11

1 swing = 13/10 = 1.3 s
uncertainty = 0.3/10 = 0.03 s
Time = 1.3 +- 0.003 s

Question 12

What is the difference reading and measurement?

Answer 12

Readings are when one value is found, measurements are when the difference between two readings is found.

Question 13

What is the uncertainty of a thermometer whose smallest division is 5 degree celcius?

Answer 13

The uncertainty in a reading is +- half the smallest division, so uncertainty is +- 5/2 or +- 2.5 degree celcius.

Question 14

What is the uncertainty in the charge of an electron (1.6 x 10^-19C) ?

Answer 14

The uncertainty in a given values is +- the last significant digit: = 1.6 x 10^-19 +- 0.1 x 10^-19 C

Question 15

what is the mean and absolute uncertainty of ball to drop are 3.2s, 3.6s, and 3.1s?

Answer 15

Mean = (3.1 + 3.2 + 3.6) / 2 = 3.3 s
Absolute uncertainty = Half the range (3.6 - 3.1) / 2 = 0.25 ~ 0.3s (1 s.f)
3.3 +- 0.3s

Question 16

what is speed, equation of speed and SI units?

Answer 16

Speed is the rate of change of distance.
The equation = distance / time take
SI units = ms^-1

Question 17

What is displacement?

Answer 17

Displacement is the distance it has travelled in a given direction, so it is a vector with both magnitude and direction.

Question 18

What is velocity, equation of velocity, and SI units?

Answer 18

Velocity is rate of change of displacement or speed in a given direction, making velocity a vector.
The equation = change in displacement/time
SI units = ms^-1

Question 19

What is acceleration, equation of acceleration and SI units?

Answer 19

Acceleration is the rate of change of velocity, making it a vector.
The equation = change in velocity / time
SI units are ms^-2

Question 20

What is straight, horizontal line represent on a displacement-time graph and velocity -time graph?

Answer 20

Displacement-time : a stationary object.
Velocity-time : An object moving with constant velocity.

Question 21

What does line with a constant, non-zero gradient represent on displacement-time graph and velocity-time graph?

Answer 21

Displacement-time : an object moving with constant velocity.
Velocity-time : an object that is accelerating (positive gradient of decelerating (negative gradient).

Question 22

What does curved line represent on a displacement-time graph?

Answer 22

Acceleration (if gradient is increasing) or deceleration (if gradient is decreasing)

Question 23

What does the area under a velocity-time graph and acceleration-time graph represent?

Answer 23

Velocity-time : Displacement
Acceleration-time : Velocity

Question 24

Which way does gravity act?

Answer 24

downward

Question 25

What is free fall?

Answer 25

An object dropped in air experiences no air resistance.

Question 26

1 kg rock and 10 kg small boulder are dropped from the back of a truck at the same time. Which will hit the ground first?

Answer 26

Both of them dropped at the same time.

Question 27

What is gravity?

Answer 27

When an object is in free fall.

Question 28

What is freely falling objects?

Answer 28

Fall with same acceleration, net force acting on them is weight, their weight-to-mass ratios are always the same, their acceleration is g, the acceleration due to gravity.

Question 29

What factor effects the amount of air resistance experienced by an object?

Answer 29

Surface and speed of object through air.

Question 30

What is projectile?

Answer 30

Projectile is particle that moves freely under gravity in two-dimensional plane.

Question 31

What is time of flight of projectile?

Answer 31

The time of flight of projectile is the total time it is in the air.

Question 32

What is range?

Answer 32

Range is the horizontal distance it travels.

Question 33

What is maximum height attained by projectile?

Answer 33

The maximum height attained by projectile is momentarily at rest, where the vertical velocity component equals zero.

Question 34

True or false? The vertical velocity component of an object in projectile motion at maximum height is zero.

Answer 34

True

Question 35

What is equation of vertical compent in projectile motion?

Answer 35

Vy= U sin theta

Question 36

What is equation of horizontal component in projectile motion?

Answer 36

Vx = U Cos theta

Question 37

what is vertical component of acceleration of an object in projectile motion?

Answer 37

The vertical component of acceleration of projectile is the acceleration due to gravity.

Question 38

The measurement error that lead to uncertainty is ?

Answer 38

Systematic error. Random error.

Question 39

What is the difference between systematic error and random error?

Answer 39

systematic error : measurements may be precise, but not accurate. --> using a stretched measuring tape, scale that always reads to high or low, reading an indicator from a poor angle. random error : measurements lack precision, but cluster around accurate value. --> timing depends on reaction time, people take turns taking readings, rounding values up or down.

Question 40

What is zero errors?

Answer 40

Type of systematic error which occurs when an instruments gives a reading when the true reading is zero. For example, the balance starts at 2 g instead of 0 g.

Question 41

How to reduce reading error?

Answer 41

Use more precise device with smaller measuring intervals and therefore less uncertainty.

Question 42

What is parallax error?

Answer 42

Occurs due to incorrect positioning of the eyes while taking a reading on a measuring scale. If the viewing angle is not perpendicular to the scale at the point where we are taking the reading, we will get less or more value of the measurement than actual value.

Question 43

What is the types of uncertainty?

Answer 43

1. Degree of uncertainty when measurements are taken 2. It not the same as errors : errors can be occur through equipment or methology that cause reading to be different from the true value, while uncertainty is range of values around a measurement within which true value is expected to lie, and is an estimate.

Question 44

What is absolute uncertainty, fractional uncertainty, and percentage uncertainty?

Answer 44

Absolute uncertainty is given as fixed quantity. absolute uncertainty = 1/2 x 0.2 mA = 0.1 mA --> I = 1.6 +- 1/16mA Fractional uncertainty is givem as fraction of the measurment. Percentage uncertainty is given as percentage of the measurent. Percentage uncertainty = (uncertainty/measured value) x 100%

Question 45

How to find uncertainty in reading, repeated data, and digital readings?

Answer 45

reading: +- half the smallest division repeated data: +- 1/2 (largest-smallest value) digital reading: +- the last significant digit unless otherwise quoted. Note: -Make sure that the number of significant figures is the same as reading. - Absolute uncertainties (denoted by triangle) have the same units as the quantity. - The uncertainty is constants, such as (phi), is taken to be zero.

Question 46

How to do propagating uncertainties / combining uncertainties?

Answer 46

1. Adding/subtracting data: add together he absolute uncertainties --> d1= 55.0 +- 0.5 cm & d2= 21.0 +- 0.7 cm --> 55.0-21.0 = 34.0 cm --> +-(0.5+0.7) = +- 1.2 cm --> 34.0 +- 1.2 cm 2. Multiplying / dividing data: D= 50.0 +- 0.1 m & T= 5.00 +- 0.05 s --> s=d/t --> s=50.0/5.0=10.0 ms^-1 --> triangle v/v = triangle s/s + triangle t/t --> 0.1/50.0 + 0.05/5.00 = 0.002 + 0.01 = 0.012 --> absolute uncertainty (change of velocity) = 10.0 x 0.012 = +- 0.12 ms^-1 --> v = 10.0 +- 0.012 ms^-1 3. Multiply the percentage uncertainty by the power: V = 4/3(phi)r^3 --> r = 2.50 +- 0.02 cm --> V = 4/3(phi)(2.50)^3 = 65.5 cm^3 --> triangle V/V = 3 x triangle r/r = 3 x 0.02/2.50 = 0.024 --> absolute uncertainty (triangle V)+ 65.5 x 0.024 = 1.57 cm^3 -- percentage uncertainty (%triangle V)= 100 x 0.024 = 2.4%

Question 47

How to calculate uncertainty in gradient?

Answer 47

The line of best fit should be drawn on the graph: the 'best' line of best fit, which passes as close to the points as possible, the 'worst' line of best fit, either the steepest possible or the shallowest possible line which fits within all the error bars.

Question 48

What is the percentage uncertainty in the graph?

Answer 48

1. We can use gradient to find the percentage uncertainty: Percentage =( (best gradient - worst gradient) / best gradient) x 100% 2. We can also use the average of two min and max to find percentage uncertainty: percentage uncertainty = ((max. gradient - min. gradient) / 2) x 100% 3. We can use the y-intercept to find percentage uncertainty: percentage uncertainty = ((best y intercept - worst y intercept) / best y intercept) x 100% percentage uncertainty = ((max. y intercept -min. y intercept) / 2) x 100%

Question 49

What is percentage difference and how to find percentage difference?

Answer 49

Percentage difference gives indication of how close the experimental value achieved from an experiment is to the accepted value. percentage difference is not the same as percentage uncertainty. Percentage difference = ((experimental value - accepted value) / accepted value) x 100%

Question 50

What is experimental value and accepted value?

Answer 50

Experimental value is refer as the measurement value. While accepted value is refered as true value. Note: The smaller the percentage difference, the more accurate the results of the experiment.

Question 51

True or False! Two object side by side must have the same speed.

Answer 51

False, because there is also an object that start from 0 or start more than 0.

Question 52

True and False! Acceleration and velocity are always in the same direction.

Answer 52

False, because sometimes acceleration might go to the negative while velocity go to the positive and acceleration might also go to positive but velocity go to negative.

Question 53

True and False! If velocity is zero, then acceleration must be zero too.

Answer 53

False. Because when an object is thrown up and experiences free fall, it is constantly accelerating a 10 m/s^2. However, at its highest point, its velocity is zero.

Question 54

True or False! Inertia is the force that keeps objects in motion.

Answer 54

False, because inertia is not a force. It is property/characteristic of the object or system determined by the mass distribution.

Question 55

True and False! All objects eventually stop moving when a net force is removed.

Answer 55

False, because an object's inertia (mass distribution) resists any change in motion including a change in velocity.

Question 56

What is scalar quantities and vector quantities?

Answer 56

Scalar quantities: only have magnitude. For example, distance and speed. Vector quantities: both have magnitude and direction. For example, velocity, displacement, and acceleration. Note: In physics, symbol triangle means change.

Question 57

How do you solving problem with kinematic equations?

Answer 57

Step 1: write out the variables that are given, both known and unknown. Step 2: choose the equation that contains the quantities you have listed. Step 3: Convert any units to SI units and the insert the quantities into the equation and rearrange algebraically to determine the answer.

Question 58

What is independent variable, dependent variable, and control variable in free fall experiment?

Answer 58

1. Independent variable is the height 2. Dependent variable is time. 3. Control variable is same electromagnet, same steel ball-bearing, and distance between ball-bearing and top of the glass tube.

Question 59

What is the source of error in free fall experiment?

Answer 59

1. Systematic error: residue magnetism after the electromagnet is switched off may cause the time to be recorded as longer than it should be. 2. Random error: large uncertainty in distance from using a metre rule with a precision of 1mm, parallax error reading h, tha ball may not fall accurately down the centre of each light gate, it can be reduced through repeating the experiment.

Question 60

What need to be safety considerate in free fall experiment?

Answer 60

1. The electromagnetic require to be taken to not have any water near it. 2. Switch on the current to the electromagnet once to reduce risk of electrocution. 3. A cushion need it to catch the ball, so it doesn't roll or damage the surface. 4. the tall clamp stand need to be attach with G clamp so it stays rigid.

Question 61

Why in vacuum both feather and apple falls at the same rate?

Answer 61

Because in vacuum, there is no air, which means there is no air resistance. So surface area and mass makes no difference.

Question 61

Is free fall means that the object is falling down only?

Answer 61

No, free fall is not falling down only. The objects thrown upward or downward and those released from rest are all the example of free fall.

Question 62

What is mean by acceleration due to gravity?

Answer 62

It means that the ball speed change in each second, the reason of change in speed is due to gravity. Which is why it is called as acceleration due to gravity.

Question 63

What is projectile motion?

Answer 63

It is the motion of an object thrown (projected) into the air when, after the intial force that lauches the object, air resistance is negligible and the only other force that object experiences is the force of gravity. Note: The object is called projectile, and its path is called trajectory.

Question 64

Is projectile motion two-dimensional motion or three-dimensional motion?

Answer 64

It is two-dimensional motion due to the external force and gravity. Projectile motion of any object is parabola.

Question 65

Two object are released from the same height. Object A fall straight down while object B follows curved parabolic path. Which of them will hit the ground first?

Answer 65

A and B hit the ground at the same time. Because both of them are released from same height. In the absence of any external forces such as air resistance, object will fall towards the ground with the same acceleration due to gravity. Therefore, object will take same amount of time to reach the ground, regardless of their paths or weights.

Question 66

At what angle to get the greatest range?

Answer 66

45 degree, because it have maximum horizontal distance travelled due to combination of initial velocity and force of gravity. If we choose angle greater than 45 degree, the vertical component of velocity will be increase cause object to spend more time in the air and reducing its horizontal distance.