ACHIEVERS MATHS, SCIENCE AND TECHNOLOGY ACADEMY(AMSTA)
ALL LEARNERS CAN LEARN
MECHANICS WORKSHEET# 2: FORCES AND NEWTON’S LAWS
ACTIVITY 1: NEWTON’S THRID LAW OF MOTION: 2023
1.
State Newton’s third Law of Motion in.
1.1 words.
1.2 Symbols.
2.
List 4 characteristics of N3 pairs of forces (action reaction pairs).
3.
Identify TWO action-reaction pairs for each of the following scenarios.
3.1 Book placed by Amaad on a table.
3.2 Wongani sitting on a chair.
3.3 Lesedi pulling a stunt between a tractor and an elephant.
(2)
(1)
(4)
(2)
(2)
(2)
[13]
5. Consider masses X (4kg) and Y(20kg) below placed in contact on a smooth surface by Makokong.
5.1
5.2
5.3
Kisho pushes mass X with a force of 36N.
State Newton’s second Law in words.
Draw a free body diagram showing all the forces acting on…
5.2.1 mass X
5.2.2 mass Y
Calculate the…
5.3.1 acceleration of the system.
5.3.2 magnitude and direction of the force mass X exerts on Y.
1
(2)
(4)
(3)
(5)
(2)
[16]
21/07/2021
6. In the diagram below Thato pushes two blocks A(5kg) and B(10kg) to the right on a rough surface as
shown in the diagram below.
6.1
6.2
6.3
6.4
6.5
State Newton’s Third Law of motion in words.
Draw a force diagram showing all the forces acting on the…
6.2.1 5kg mass
6.2.2 10kg mass
Determine the frictional force acting on…
6.3.1 5kg mass.
6.3.2 10kg mass.
Determine the…
6.4.1 the acceleration of the system.
6.4.2 the magnitude and direction of the force A exerts on B.
Tazeem says the 10kg will “bully” the smaller mass by exerting a larger force on it.
Evaluate this statement and give a reason supporting your answer.
(2)
(5)
(5)
(3)
(3)
(5)
(2)
(2)
[27]
ACTIVITY 2 : APPLICATION OF N1,N2 AND N3
1.Londolani pulls two blocks attached with a string on a rough surface as shown below.
1.1
1.2
1.3
The 2kg and the 4kg block experience frictional forces of 6N and 8N respectively. A
State Newton’s second Law in words.
Draw a free body diagram showing all the forces acting on the …mass
1.2.1 2kg
1.2.2 4kg
Calculate the…
1.3.1 acceleration of the system.
1.3.2 magnitude and direction of the tension on 2kg.
2
(2)
(5)
(4)
(5)
(2)
[18]
Question 2
Katlego now pulls the 2kg and 4kg block used by Londolani on an inclined
plane Khodani set at 300 as shown in the diagram below.
2.1
2.2
2.3
Assume the string connecting the blocks is weightless and inextensible. The blocks are
pulled up the incline with a force of 30N.
State Newton’s Second Law of motion in words.
Draw a free-body diagram showing all the forces acting on the
2.2.1 4kg body.
2.2.2 2kg body.
Determine the…
2.3.1 magnitude of the tension.
2.3.2 co-efficient of kinetic friction between the 4kg block and the surface.
3
(2)
(5)
(4)
(7)
(4)
[20]
Question 3: 23/07/2021
Two blocks, A(4kg) and B(6kg) are connected by a light inextensible string over a frictionless pulley as
shown in the diagram below.
The frictional force between the 4kg mass and the surface is 18,8N.
3.1
Draw a free-body diagram showing all the forces acting on the...mass.
3.1.1 4kg.
3.1.2 6kg.
3.2
Name the law that you can use to determine the acceleration of the system.
3.3
Determine the tension of the system.
(4)
(2)
(1)
(7)
[14]
Question 4
A 5 kg block, resting on a rough horizontal table, is connected by a light inextensible string passing
over a light frictionless pulley to another block of mass 2 kg. The 2 kg block hangs vertically as
shown in the diagram below.
A force of 60 N is applied to the 5 kg block at an angle of 10o to the horizontal, causing the
block to accelerate to the left. The coefficient of kinetic friction between the 5 kg block and the surface
of the table is 0,5. Ignore the effects of air friction.
4.1
4.2
4.3
Draw a labelled free-body diagram showing ALL the forces acting on the …body.
4.1.1 5kg
4.1.2 2kg
Calculate the magnitude of the
4.2.1 vertical component of F.
4.2.2 horizontal component F.
4.2.3 normal force acting on the block.
State Newton’s Second Law of motion in words.
4
(5)
(2)
(2)
(2)
(2)
(2)
4.4
4.5
Determine the tension in the string.
The string between 2kg and pully is 100cm long. Determine time it will take the 2kg mass
to reach pulley assuming it was initially at rest.
5
(7)
(3)
[25]
Question 5
Consider m1(2kg) and m2(4kg) held at rest. Connected by a light inextensible string over a frictionless
pulley.
m2 is now released. Ignore the effects of air friction
5.1
Draw a free body diagram showing all the forces acting on
5.1.1 m2.
5.1.2 m1.
5.2
Determine the tension in the string.
5.3
Write down the magnitude and direction of the acceleration each mass will experience
when the string is broken.
(2)
(2)
(5)
(2)
[11]
Question 6
Consider the system of masses below connected by a light inextensible string. They are hoisted
upwards by force F .
6.1
6.2
6.3
…
6.4
The effects of air friction can be ignored. The acceleration of the system is 0,2m.s-2
State Newton’s First Law of motion in words.
Draw a free body diagram showing all the forces acting on …
6.2.1 A
6.2.2 B
Determine the magnitude of…
6.3.1 T1
6.3.2
Write down the magnitude of F and name of the law you used to arrive at your answer.
6
(3)
(2)
(4)
(3)
(2)
[14]
Question 7
Two satellites orbiting the earth are located on opposite sides of the Earth. Satellite A has a mass of 3 800kg
and Satellite B has a mass of 4 500kg.Satelite B is on the surface of the earth. The mass of the earth is
5,98x1024kg and the radius of the earth is 6,38 x106m.
Earth
Satellite A Satellite B
Satellite A is 25 00km above the surface of the earth.
7.1 State the universal law of gravitation in words.
7.2 Prove that acceleration due to gravity on the surface of the earth is 9,8m.s.-1 (3)
7.3 Sate the Universal Law of gravitation in symbols. (2)
7.4 Determine the gravitational force the earth exerts on ..
7.5 Satellite A. (4)
7.6 Satellite C. (4)[13]
7