Topic 1- General Physics

Question 1

define density (unit)

Answer 1

mass per unit volume of a given object

ρ= density, kg/m^3  
m= mass, kg
V= volume, m^3
ρ = m/ V

Question 2

define weight (unit)

Answer 2

Weight is the effect of a gravitational field on a mass

Question 3

define speed (unit)

Answer 3

distance covered per unit of time (m/s)

The speed of an object is the magnitude of the change of its position; it is thus a scalar quantity.

Question 4

describe the difference between scalar and vector quantities

Answer 4

vectors have a magnitude and direction

scalars only have a magnitude

Question 5

give examples of scalar and vector quantities

Answer 5

scalar- distance, speed, mass,

vector- displacement, velocity, weight, acceleration

Question 6

what is used to measure length

Answer 6

Longer distances- measuring tape (typically to 1cm)
Ruler (to 1mm, eg. 7.4 cm)
Vernier calipers (to 0.1mm, eg. 7.4mm)
Micrometer screw gauge (to 0.01 mm, eg. 7.42 mm)

Question 7

define acceleration

Answer 7

a= (v-u )/t
or a= Δv/t

acceleration= change in velocity/time

Question 8

describe difference of displacement and distance

Answer 8

Distance- scalar quantity that refers to “how much ground an object has covered” during its motion.

Displacement- vector quantity that refers to “how far out of place an object is”; it is the object’s overall change in position.

Question 9

what is g

Answer 9

the acceleration due to gravity (9.8 m/s^2 near Earth)

or gravitational field (9.8 N/kg near Earth)

Question 10

why is the gravitational pull of different bodies different

Answer 10

Gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases.

Question 11

describe free fall acceleration

Answer 11

in the absence of air resistance, a free-falling object has an acceleration of 10 m/s/s, downward (on Earth)

Question 12

what is used to measure length

Answer 12

Longer distances- measuring tape (typically to 1cm)
Ruler (to 1mm, eg. 7.4 cm)
Vernier calipers (to 0.01mm, eg. 7.4mm)
Micrometer screw gauge (to 0.001 mm, eg. 7.42 mm)

Question 13

what is the zero error

Answer 13

when the measuring instrument registers a reading when there should not be any reading

Question 14

what is used to measure time

Answer 14

stopwatch

Question 15

SI base unit and other units for time

Answer 15

base- seconds (s)

1 ms= 10^-2 s
1 µs= 10^-6 s
1 ns = 10^-9 s

Question 16

how would you accurately measure the thickness of a very thin object (eg. paper) and the mass of a very light object (eg. paper clips)

Answer 16

measure the thickness of multiple sheets/ the mass of multiple clips and divide it by the number

Question 17

when the acceleration is constant, what will the velocity time graph look like

Answer 17

the velocity will increase as a linear function

for constant acceleration there is linear motion

Question 18

how would you calculate the distanced travelled for motion with constant acceleration

Answer 18

Calculate the area under a speed-time graph

Question 19

difference between weight and mass

Answer 19

Weight depends on the gravitational field of the mass, meaning that it can change (N)
Mass is amount of matter in an object and always remains the same (kg)

Question 20

How can you tell whether an object will float based on density data

Answer 20

Density of object < density of liquid = float

Question 21

Describe an experiment to determine the density of a liquid and of a regularly shaped solid and make the necessary calculation

Answer 21

Regularly shaped solid:
1. Calculate the volume:
cuboid= lwh
cylinder = π r^2h

2. Find the mass using an electric balance
3. Divide mass by volume

Liquid

1. Pour liquid into measuring cylinder. The level on the scale is the volume.
2. Measure the mass of the water with the cylinder then the mass of the cylinder without the liquid. Subtract the latter value from the former.
3. Divide mass by volume

Question 22

Describe the determination of the density of an irregularly shaped solid by the method of displacement

Answer 22

1. Lower the solid into a partially filled measuring cylinder. The rise in the level on the volume is the volume of the solid.
2. Find the mass of the solid.
3. Divide mass by the volume
   * if the solid floats, you can add a weight on top to submerge it (remember to subtract its volume from the step 1)

Question 23

How do you calculate change in velocity from a graph

Answer 23

Find the area under an acceleration graph which represents the change in velocity

Question 24

what is the difference between speed and velocity

Answer 24

Speed- scalar; rate at which an object covers distance. Velocity- vector; it is direction-aware; rate at which the position changes.

Question 25

Describe qualitatively the motion of bodies falling in a uniform gravitational field with and without air resistance (including reference to terminal velocity)

Answer 25

1. Initially acceleration is g (no/little speed).
2. As speed increases, air resistance increases.
3. Eventually air resistance is enough to balance weight.
   When this happens, velocity reaches its maximum and stays constant.

Question 26

How can weights (and hence masses) may be compared using a balance

Answer 26

The balance compares the weight, where weight is the downward pull of gravity. The beam balance balances when the downward pull on both pans are equal. However, the masses can also be compared because of the way gravity acts on them.
If the objects on the two pans have the same weight, they have the same mass.

Question 27

How do you calculate change in velocity from a graph

Answer 27

Find the area under an acceleration graph which represents the change in velocity

Question 28

Describe qualitatively the motion of bodies falling in a uniform gravitational field without air resistance.

(eg. ball thrown up)

Answer 28

1. As ball is thrown upwards, downward (negative) velocity increases by 10m/s each second.
   eg. Ball thrown upwards with a velocity of 30m/s, g=10m/s^2

0s= 30m/s, downward velocity is -30m/s
1s= 20m/s, downward velocity is -20m/s
2s= 10 m/s
3s= 0 m/s 
4s= 10m/s
5s= 20m/s downward velocity is 20m/s
6s= 30m/s 
10m/s is being added to the downward velocity every second

2. As ball reaches highest point, downward velocity becomes 0m/s.
3. Downward velocity increases by 10m/s each second still as the ball falls.
4. Ball eventually has the same speed that it had to begin with, except in the opposite direction.

velocity-time graph line: / across the x axis (eg. from (0,-30) to (6,30)

Question 29

a negative acceleration is called __?

Answer 29

deceleration

Question 30

how would you use the dots in ticker tape to describe the motion of a trolley

Answer 30

far apart- faster speed

closer together- slower speed

Question 31

how would you calculate volume? formula

Answer 31

V=m/p

mass/ density

Question 32

An object falls at a speed of 𝑥 m/s where air resistance is negligible. How would you calculate the time taken for the object to reach the ground?

Answer 32

acceleration = change in velocity/time
a= Δv/t
Δv= x-0 (starts with 0m/s)
a= 10 m/s^2 in this case the acceleration is g, gravitational field strength

We are trying to find t
t= v/g
in this case time taken (s) = 𝑥 (m/s) ÷ 10 (m/s^2)

Question 33

An object made of metal A sinks in oil. How would attaching a piece of wood prevent this object from sinking.

Answer 33

The average density of the wood and the object is less than the density of oil

Question 34

A student has 500 sheets of paper.
The surface area of 1 sheet is 0.063m^2.
1m^2 of the paper has a mass of 0.08kg

What is the mass of one sheet of paper.

Answer 34

ANSWER= Mass of 1 paper is 5.04*10^-3 kg

Divide 0.08kg by the number of sheets in 1m^2

1. How many sheets is in 1m^2 of paper?
   1 ÷0.063= 15.87
2. Divide the mass of 1m^2 of the paper by the number of sheets that makes it up (15.87)
3. 08 ÷ 15.87 = 5.04*10^-3

Question 35

Student A has 500 sheets of paper.
Student B has 5 sheets of paper.
How can student B determine the density of the paper to a similar accuracy? (Additional apparatus may be used)
2pt

Answer 35

They can use electronic calipers/ micrometer to measure the thickness of the paper (in a pile, then divide it by 5)
Then they can use an electronic balance to find its mass

Question 36

How would you calculate (constant) acceleration from a velocity time graph?

Answer 36

a= Δv/t

Find the velocity on the y axis and divide it by time on the x axis