practice question


QUESTION 2

2.1. A person pushes a lawnmower of mass 15 kg at a constant speed in a straight line over a flat grass surface with a force of 90 N. The force is directed along the handle of the lawnmower. The handle has been set at an angle of 40° to the horizontal. Refer to the diagram below. 
2.1.1 Draw a labelled free-body diagram for the lawnmower.  (4)

2.1.2. Why is it CORRECT to say that the moving lawnmower is in equilibrium?  (1) 
2.1.3. Calculate the magnitude of the frictional force acting between the
lawnmower and the grass  (3) 

The lawnmower is now brought to a stop. 
2.1.4. Calculate the magnitude of the constant force that must be applied through the handle in order to accelerate the lawnmower from rest to 2 m∙s-1 in a time of 3 s. Assume that the frictional force between the lawnmower and grass remains the same as in QUESTION 2.1.3. (6)


2.2. Planet Y has a radius of 6 x 10^5 m. A 10 kg mass weighs 20 N on the surface of planet Y
Calculate the mass of planet Y.  (4)

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grade 12 acid and base questions


QUESTION 7 (Start on a new page.)


7.1 Nitric acid (HNO3), an important acid used in industry, is a strong acid.
7.1.1 Give a reason why nitric acid is classified as a strong acid. (1)
7.1.2 Write down the NAME or FORMULA of the conjugate base of nitric acid. (1)
7.1.3 Calculate the pH of a 0,3 mol∙dm-3 nitric acid solution. (3)
7.2 A laboratory technician wants to determine the percentage purity of magnesium oxide. He dissolves a 4,5 g sample of the magnesium oxide in 100 cm3 hydrochloric acid of concentration 2 mol∙dm-3
.
7.2.1 Calculate the number of moles of hydrochloric acid added to the magnesium oxide. (3)
He then uses the apparatus below to titrate the EXCESS hydrochloric acid in the above solution against a sodium hydroxide solution

7.2.2 Write down the name of apparatus Q in the above diagram. (1)
7.2.3 The following indicators are available for the titration:

Which ONE of the above indicators (A, B or C) is most suitable to indicate the exact endpoint in this titration? Give a reason for the answer. (3)

7.2.4 During the titration, the technician uses distilled water to wash any sodium hydroxide spilled against the sides of the Erlenmeyer flask into the solution.
Give a reason why the addition of distilled water to the Erlenmeyer flask will not influence the results. (1)
7.2.5 At the endpoint of the titration he finds that 21 cm3 of a 0,2 mol dm-3 sodium hydroxide solution has neutralised the EXCESS hydrochloric acid. Calculate the number of moles of hydrochloric acid in excess. (3)
7.2.6 The balanced equation for the reaction between hydrochloric acid and magnesium oxide is:
MgO(s) + 2HCℓ(aq) → MgCℓ2(aq) + 2H2O(ℓ)
Calculate the percentage purity of the magnesium oxide. Assume that only the magnesium oxide in the 4,5 g sample reacted with the acid. (5)
[21]

grade 10 test yourself


7.1 The following table gives a range of electric circuit components and their symbols. Study
the table and answer the questions that follow: (14)

7.1.1 Which ONE of the above components cannot be connected in series with other components?
(2)
7.1.2 An ammeter measures the electrical current of an electric circuit. Define the term ’electrical current’ (2)
7.1.3 A conductor that resists the flow of electrical current is called a ‘resistor’. Name two factors which influences the resistance of a conductor. (4)

7.2. A group of learners were doing some investigation.They wanted to measure the voltmeter reading across a battery of 2 cells, when this battery is connected to a resistor. They also wanted to measure the current flowing through the circuit.They connected the components as shown in the
diagram.

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Their teacher saw the connections and said that there are two major mistakes in the connection.Their teacher drew a correct circuit diagram for the learners so that they can do the investigation.

7.2.1 Mention the two major mistakes in the connection made by learners. (2)
7.2.2 Draw the correct circuit diagram that the teacher drew for the learners, where there
are no major mistakes. Include a switch in the circuit diagram.
(4)

TOTAL [14]

GRADE 12 TEST YOURSELF


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.

1. Draw a labelled free-body diagram showing ALL the forces acting on the 5 kg block. (5)

2. Calculate the magnitude of the:

2.1. Vertical component of the 60 N force (2)
2.2.Horizontal component of the 60 N force (2)
2.3. State Newton’s Second Law of Motion in words. (2)

3. Calculate the magnitude of the:

3.1.Normal force acting on the 5 kg block (2)
3.2.Tension in the string connecting the two blocks (7)
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