capítulo 5. mass, weight and density

Fsica 9 de secundaria

1 Profesor: Javier Trigoso T.

Captulo 5

MASS, WEIGHT & DENSITY

Mass Weight

Definition Measure of the amount of

matter in a body

Amount of gravitational

force acting on a body

SI Unit Kilogram (kg) Newton (N)

Properties

Mass has only magnitude,

and is constant

(unaffected by

gravitational field strength)

Weight has both

magnitude and direction

(towards the centre of

Earth)

Relationship Weight of an object is directly proportional to its mass.

W = m g

Gravitational field strength (g) is the gravitational force acting per unit mass on an

object. (SI: N/kg). On the surface of Earth, the acceleration caused by gravity is 9.81

m/s2, approximately.

VOLUME. Measures the Space Occupied by a body. (SI: m3)

Examples: Cube: 3V Sphere: 34

V R3 Cylinder: 2V R h

DENSITY. Density is the mass per unit volume of a substance. The equation for

determining density is m

V (SI: kg/m3)

Use g = 10 m/s2

01. A man has a mass of 66 kg on Earth.

What is his weight in Newton?

660 N

02. Neil weighs 750 Newton (750 N) on

Earth. On the planet Mars, the force

of gravity is 38% of that on Earth.

How much would Neil weigh on

Mars?

285 N

03. Buzz has a mass of 70 kg. What is his

weight on the Earth (in Newton)?

700 N

04. Valentina has a mass of 55 kg.

What is her weight on Mars, where

the gravitational force is 3.72 N/kg,

to the nearest whole number?

205 N

05. Luke weighs 980 N on Earth and 370

N on the planet Mercury.

What is the gravitational force on

Mercury?

3.7 N/kg

06. The ratio of the gravitational force

on the Moon to the gravitational

force on Earth is 1:6. James has a

mass of 84 kg on Earth.

What is his mass on the Moon?

84 kg

07. A wax candle has a volume of 1,000

ml. The candle has a mass of 1.4 kg

(1,400 g). What is the density of the

candle?

1.4 g/ml



08. The diagram shows a material with

dimensions 5 cm 4 cm 2 cm. I has

a mass of 100 g. What is your

density?

2.5 g/cm3

09. A cube has a side of 5 cm. It has a

mass of 250 grams. The density of the

cube is:

2.0 g/cm3

10. A block of aluminum occupies a

volume of 15.0 ml and weighs 40.5 g.

What is its density?

2.7 g/ml

11. A student measures the mass of five

steel nuts to be 96.2 g. The nuts

displace 13 ml of water. Calculate

the density of the steel in the nuts

7.4 g/cm3

12. Ten identical steel balls, each of

mass 27 g, are immersed in a

measuring cylinder containing

20 cm3 of water. The reading of the

water level rises to 50 cm3. What is the density of the steel?

9.0 g/cm3

13. A rectangular block of copper metal

weighs 1896 g. The dimensions of the

block are 8.4 cm by 5.5 cm by 4.6

cm. From this data, what is the

density of copper?

8.9 g/cm3

14. An irregular object with a mass of

118 g displaces 25 ml of water when

placed in a graduated cylinder.

Calculate the density of the object

4.72 g/ml

15. A bead weights 15 g. You place it in

a graduated cylinder that has 20 ml

of water in it. After placing the bead

in the cylinder, the water level is now

at 30 ml. What is its density?

1.5 g/ml

16. A 4,500 g. cube of titanium is 10

centimeters on each side. Calculate

its volume in cm3, and then

calculate its density in g/cm3

1000 cm3, 4.5 g/cm3

17. A wooden block of dimension 1

m 1 m 1 m has a mass of 800 kg.

Ajay attached a steel plate of

dimension 1 m 1 m 0.02 m to the

block. Given that the steel plate has

a mass of 140 kg, what is the density

of the combination in kg/m3?

922 kg/m3

18. Godzilla was running wild in Brigham

City but was finally captured. The

Police Department needs you to tell

them his density (the FBI must know

this). You have a huge vat of water

filled to the 1,000 L level. You drop

the kicking and roaring Godzilla into

the vat. It now reads 2,716 L. At the

bottom of your vat is a scale. You

empty the water and weigh Godzilla

His mass is 8,000kg. What is his

density?

4.662 kg/ml



MASS, WEIGHT & DENSITY

01. Mass is:

A. The amount of matter in an

object

B. The amount of matter in a small

amount of space

C. The amount of matter plus the

volume

D. The amount of matter that makes

an object more dense

02. How is mass different than weight?

A. Mass and weight are not any

different. They are exactly the

same

B. Mass is the amount of matter and

weight is the amount of matter

plus electricity

C. Mass is the amount of matter and


plus energy

D. Mass is the amount of matter and


plus gravity

03. The formula for finding density is:

A. The volume divided by the mass

B. The mass multiplied by the

volume

C. The mass divided by the volume

D. The volume multiplied by the

mass

04. You are given a mystery object in

science class. Your teacher asks you

to determine if your object is more or

less dense than water. You place the

object in the water and it sinks. What

statement would best describe this

situation?

A. The mystery substance is denser

than water

B. Water is denser than the mystery

substance

C. They both have the same mass

D. The mystery substance must be

hollow

05. You have two plastic glasses. One

contains 40 ml of water and the

other contains 40 ml of alcohol.

Which statement is correct?

A. Both glasses have the same

density

B. Both glasses have the same

volume

C. Both glasses have the same mass

D. All of the above

06. The mass of a rock on the Earth is 2.0

kg. What is the mass of the rock on

the Moon?

A. 1.7 kg

B. 2.0 kg

C. 3.4 kg

D. 20 kg

07. The mass of a rock on the Earth is 2.0

kg. What is the weight of the rock on

the Moon?

A. 1.7 N

B. 2.0 N

C. 3.4 N

D. 20 N

08. The weight of a rock on the Earth is

20 N. What is the weight of the rock

on the Moon?

A. 2.0 N



B. 3.4 N

C. 12 N

D. 20 N

09. The weight of a rock on the Moon is

200 N. What is the mass of the rock

on the Earth?

A. 20 kg

B. 118 kg

C. 200 kg

D. 1180 kg

10. The weight of a rock on the Moon is

200 N. What is the weight of the rock

on the Earth?

A. 20 N

B. 118 N

C. 200 N

D. 1180 N

11. The weight of three objects

measured on three celestial bodies

are listed below. The weight of

object A on the Moon is 200 N. The

weight of object B on Jupiter is 6000

N. The weight of object C on

Mercury is 400 N. Which of the

following sequence shows the mass

of the three objects in ascending

order? (The acceleration due to

gravity of the Moon, Jupiter and

Mercury are 1.7 m s-2, 25.4 m s-2 and

3.8 m s-2 respectively)

A. object A, object B, object C

B. object C, object A, object B

C. object A, object C , object B

D. object B, object C, object A

12. An astronaut of mass 80 kg jumped

out of the rocket after it had landed

on Jupiter. The astronaut took 0.40 s

to drop for 2.0 m. What was the

weight of the astronaut on Jupiter?

A. 800 N

B. 1000 N

C. 1800 N

D. 2000 N

13. When solid A of mass 2 g is immersed

in a measuring cylinder filled with

water, it displaces a volume of 4

cm3, what is the density of solid A?

A. 0.3 g cm-3

B. 0.5 g cm-3

C. 2 g cm-3

D. 4 g cm-3

14. The figures below show the

difference in water level before and

after solid A is submerged in

measuring cylinder. Given that solid

A is 20 g, what is the density of solid

A?

A. 0.3 g cm-3

B. 0.5 g cm-3

C. 2 g cm-3

D. 4 g cm-3

15. When solid A of mass 12 g is

immersed in a measuring cylinder

filled with water, it displaces the

same volume of water as solid B of

mass 8 g. What can be deduced

about the densities of solids A and B?

A. Both A and B have the same

density

B. Density of A is 4 times density of B

C. Density of A is 2/3 times density of

B

D. Density of A is 3/2 times density of

B

16. In an attempt to find the density of a

piece of floating object, the

following measurements were

carried out.

Figure 1: Measuring cylinder with

water.


water and a piece of stone

submerged within.


water and a piece of stone tied to



the floating object such that the

floating object is also submerged

under water.

Given that the floating object has a

mass of 3.0 g, what is its density?

A. 0.23 g cm-3

B. 0.43 g cm-3

C. 0.50 g cm-3

D. 3.50 g cm-3

17. In an attempt to find the average

mass of an iron ball, the following

measurements were carried out.


water.


water and 20 iron balls submerged

within.

Given that iron has a density of 7.5 g

cm-3, what is the mass of one iron

ball?

A. 1.87 g

B. 5.25 g

C. 16.9 g

D. 105 g

18. A bottle full of water has a mass of

200 g. When the same bottle is filled

with liquid X, the mass becomes 180

g. If the mass of the empty bottle is

100 g, what is the density of liquid X

in g cm-3? (Take the density of water

is 1.0 g cm-3)

A. 0.2 g cm-3

B. 0.8 g cm-3

C. 0.9 g cm-3

D. 1.2 g cm-3

19. A wooden block of dimension 1 m

1 m 1 m has a mass of 800 kg. Of

Ashwin sawed half of the block

away, what is the density of the

remaining wooden block in kg m-3?

A. 200 kg m-3

B. 400 kg m-3

C. 800 kg m-3

D. 1600 kg m-3

20. 5000 kg of iron is melted and mixed

with 2.0 m3 of molten copper. If the

density of molten iron and molten

copper are 7.5 g cm-3 and 9.0 g cm3

respectively, what is the

approximate density of the mixture?

A. 7.5 g cm-3

B. 8.3 g cm-3

C. 8300 kg m-3

D. 8600 kg m-3

capítulo 5. mass, weight and density

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