Workbook Worksheet 4
Section A
1C
2B
3A
4C
5.
5D
6C
7D
Working/ Explanation
Weight W Moon of object = mgMoon where m = mass of object
m = W Moon / gMoon = 34/1.7 = 20 kg
Weight W Earth of object on Earth = mgEarth = 20 x 10 = 200 N
6.
Working/ Explanation
Density of block P = mp/vp = 360/(6x4x3) = 5.0 g cm-3
Density of block Q = mq/vq = 480/ (5x4x4) = 6.0 g cm-3
Density of block R = mR/vR = 600/(5x5x3) = 8.0 g cm-3
Density of block S = ms/vs = 800/(10x5x3) = 5.3 g cm-3
Section B
1(a) Since mass is the amount of matter in a body, the mass of the apple is not affected
by its location.
1(b) Weight is the result of gravitational force acting on a body. Since the gravitational
field strength on Earth is greater than on the Moon, the weight of the apple is greater
on Earth than on the Moon.
2(a)(i) Mass is the amount of matter in a body, while inertia is the reluctance of a body to
change its state of rest or motion.
(ii) The greater the mass of a body, the greater its inertia. A truck has more mass,
therefore it has more inertia than a person.
2(b) When a vehicle comes to a sudden stop, the passenger’s body continues to move
forward due to inertia. In the event of an accident, the seat belt prevents the
passenger’s body from being thrown forward, decreasing the risk of injury or death.
2(c)
If the truck stops suddenly, the logs of wood in the truck will continue to move
forward due to inertia. If the ropes securing the logs to the truck come loose, the logs
can slide forward, causing serious injury to the passenger.
3(a)
3(b)
4(a)
4(b)
Using W = mg
weight on Earth = 70 x 10 = 700 N
weight on the Moon = 1/6 x 700 = 117 N
weight on Jupiter = 2.64 x 700 = 1850 N
Since the gravitational field strength on the Moon is lower than that on Earth, the
weight of the box will be lower on the Moon. Thus it would be easier for the man to lift
box on the Moon.
The density of a substance is its mass per unit volume.
Density = mass/volume
= 600/(10x10x10) = 0.6 g cm-3
4(c)
Volume = mass/density
= 2/7900 = 2.5 x 10-4 m3
4(d)
Mass = density x volume
= 1.25 x (6x5x3) = 112.5 kg
5(a)
Given:
mass m of copper ball = 1 kg
Density p of copper = 8900 kgm-3
Let the radius of the copper ball be r.
Volume of copper ball = 4/3πr3 = mass/density
= 1/8900 = 1.12 x 10-4 m3
r3 = (3)(1.12 x 10-4)/ 4π
r = 2.99 x 10-2 m
5(b)
Mass of mercury = 360 – 88 = 272 g
Density of mercury = mass/volume = 272/20 = 13.6 g cm-3
= 13.6 x 103 kg m-3
Section C
1(a)
The density of the expanded polystyrene is much lower than that of lead. Since
density = mass/volume and the volumes of the expanded polystyrene and lead are
equal, the mass of the piece of expanded polystyrene is much lower than that of a
piece of lead. A lower mass means a smaller weight, therefore the piece of expanded
polystyrene feels much lighter than the piece of lead.
1(b)
Given:
density of air = 1.29 kg m-3
density of oxygen = 1.43 kg m-3
3
Consider 1 m of air, which comprises 0.2 m3 of oxygen and 0.8 m3 of nitrogen.
Mass of 1 m3 of air = 1.29 kg
Mass of 0.2 m3 of oxygen = density x volume
= 1.43 x 0.2 = 0.29 kg
Mass of 0.8 m3 of nitrogen = 1.29 – 0.29 = 1 kg
Therefore density of nitrogen = mass/volume = 1/0.8 = 1.25 kg m-3
2
Planet
Earth
Moon
Mars
Jupiter
Mass of new
liquid
100g
100g
100g
100g
Gravitational
field strength
10 N kg-1
1.6 N kg-1
3.7 N kg-1
24.9 N kg-1
Volume of
new liquid
10 cm3
5 cm3
400 cm3
5000 cm3
Weight of
new liquid
1N
0.16 N
0.37 N
2.49 N
Density of
new liquid
10 g cm-3
20 g cm-3
0.25 g cm-3
0.02 g cm-3
(i)
From the formula for the gravitational field strength, g, of a planet, we can see
that g depends on the mass and radius of the planet. Since planets have different
masses and sizes, their gravitational field strengths are different.
(ii)
g = 6.67 x 10-11 x 6.0 x 1024 = 9.77 N kg-1
(6.4 x 106)2
(iii)
gJupiter = 6.67 x 10-11 x mass of Jupiter
(radius of Jupiter)2
Mass of Jupiter = gJupiter x (radius of Jupiter)2
6.67 x 10-11
= 24.9 x (7.1 x 107)2
6.67 x10-11
= 1.9 x 1027 kg