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Grade 12 Physics national exam, 2007 E.C. (2015 G.C.)
37 questions · 120 minutes. The first 5 answers are shown with explanations; sit the whole paper timed in the app to get your score and the textbook page behind every question.
- 1.Which one of the following experimental errors can be reduced by taking repeated measurements?
- A. parallel errors
- B. systematic
- C. random errors
- D. zeros errors
Answer: C. The key idea is that repeated measurements help reduce random errors. Random errors vary from one measurement to another, so averaging repeated results can reduce their effect; C is correct. A is wrong because parallel errors are not the type reduced by repeating measurements. B is wrong because systematic errors tend to shift measurements in the same way. D is wrong because repeating a measurement does not fix a zero error. Textbook: Grade 11, unit 6 · section 6.4. - 2.What is the angle between vectors $A=(ai+a\sqrt{3}j)$ units and $B=(a\sqrt{3}i+aj)$ units?
- A. 90°
- B. 60°
- C. 37°
- D. 30°
Answer: D. The angle between vectors depends on how their components point. Their dot product gives $\cos\theta=\frac{2\sqrt{3}a^2}{(2a)(2a)}=\frac{\sqrt{3}}{2}$, so $\theta=30^\circ$. A, $90^\circ$, is too large; B, $60^\circ$, is not the angle; C, $37^\circ$, is not the angle. Textbook: Grade 11, unit 2 · section 2.3. - 3.The magnitude of two vectors A and B are 12 units and 5 units, respectively. Which of the following is NOT the possible value for the magnitude of the resultant vector A + B ?
- A. 60units
- B. 17units
- C. 13units
- D. 7units
Answer: A. The key idea is that the resultant of vectors with lengths $12$ and $5$ can have a magnitude from $|12-5|=7$ to $12+5=17$. Thus $60$ units is not possible, so A is correct. B is wrong because $17$ units is possible when the vectors point in the same direction. C is wrong because $13$ units lies between $7$ and $17$. D is wrong because $7$ units is possible when the vectors point in opposite directions. Textbook: Grade 11, unit 2 · section 2.3. - 4.What is the vector product $A\times B$ of two vectors $A=7i+4j-8k$ and $B=3i-2j+5k$
- A. $36i+11j-2k$
- B. $4i+59j-26k$
- C. $-4i+59j+26K$
- D. $-36i-11j+2k$
Answer: B. Textbook: Grade 11, unit 2 · section 2.4. - 5.Which of the following statement is correct ?
- A. An object moving toward the east cannot have an acceleration toward the west.
- B. If the average velocity of an object is zero in some time interval, the average speed of the object for that time interval is also zero
- C. The velocity time graph of an object moving with constant acceleration is parallel to the time axis.
- D. An object having zero velocity can have acceleration different from zero.
Answer: D. The key idea is that velocity can be zero at an instant while acceleration is not zero. For example, at the highest point of an upward-moving object, its velocity is momentarily zero but its acceleration is still downward. A is wrong because an object moving east can accelerate west as it slows down. B is wrong because an object can return to its starting point with zero average velocity but nonzero average speed. C is wrong because constant acceleration gives a velocity-time graph with a constant slope, not generally a line parallel to the time axis. Textbook: Grade 11, unit 3 · section 3.3. - 6.A car travels along a straight line at a constant speed of 20m/s for a distance d and then another distance d in the same direction at a constant speed of 36 km/hr. what is the average speed for the entire trip?
- A. 23km/hr
- B. 48km/hr
- C. 54km/hr
- D. 60km/hr
Answer, explanation and textbook page: open in the app. - 7.If a long distance jumper athlete leaves the ground at an angle of above the horizontal surface at a speed of 10.0m/s, how far does he jump in the horizontal direction?
- A. 4.8m
- B. 6m
- C. 9.6m
- D. 9m/s
Answer, explanation and textbook page: open in the app. - 8.Women is rotating a bucket of water in a vertical circle of radius 0.9m. The mass of bucket and water is 5kg. What is the bucket's minimum speed at the top of circle if no water is to spill out?
- A. 0
- B. 1m/s
- C. 3m/s
- D. 9m/s
Answer, explanation and textbook page: open in the app.
A force of magnitude 20N is applied to a block of mass 2kg that lies on a rough, horizontal surface as shown in figure below. The coefficient of kinetic friction between the bock and surface is 0.4. What is the magnitude of the acceleration of the block? [Figure: A shaded rectangular block labelled "Block" rests on a horizontal surface drawn as a solid line with hatching beneath it (the ground). From a point on the right-hand face of the block a straight arrow points up and to the right and is labelled F at its head. A dashed horizontal line runs to the right from that same point, and the 530 angle between the dashed horizontal and the arrow F is marked .
- 9.A stray label "C(1,4)" is printed immediately after the angle; it is a scanning artifact carried over from a neighbouring figure and belongs to no part of this problem.] 10 m/s2 5.2 m/s2
- B. 4 m/s2 2.8 m/s2
Answer, explanation and textbook page: open in the app. - 10.A hard ball moving on a horizontal frictionless surface with a speed of 5m/s in the positive x direction strikes a stationary hard ball of the same mass. After the collision, the first ball moves with a speed of 4m/s along a 0.37∘ direction that makes an angle of with its initial direction of motion. What is the struck ball's speed and the smallest angle between its direction of motion and the positive x axis after the collision? 53.0∘ 37.0∘
- A. 3m/s and
- B. 3m/s and 53.0∘ 37.0∘
- C. 4m/s and
- D. 4m/s and
Answer, explanation and textbook page: open in the app. - 11.A highway curve is banked (inclined) in such a way that a car traveling at a speed of 13.5m/s can round the curve without skidding, in the absence of friction. If the banking angle is 300, what is the radius of the curve?
- A. 10.5m
- B. 21.0m
- C. 31.7m
- D. 36.7m
Answer, explanation and textbook page: open in the app. - 12.A car of mass 1500 kg is travelling at a uniform velocity of 30m/s due east. The driver applies the brakes to slow down the car to a velocity of 10m/s due east. What is the work done in slowing down the car?
- A. 15KJ
- B. 300KJ
- C. 600KJ
- D. 750KJ
Answer, explanation and textbook page: open in the app. - 13.Which one of the following statements is true about a spring mass system oscillation on a horizontal frictionless surface?
- A. The kinetic and potential energies are equal at all times.
- B. The kinetic and potential energies are both constant.
- C. The maximum potential energies is achieved when the mass passes through its equilibrium position.
- D. The maximum kinetic energy and maximum potential energy are equal.
Answer, explanation and textbook page: open in the app. - 14.A block of mass 10kg is pulled up a rough inclined plane with a force of 100N parallel to the inclined plane. The inclined plane makes an angle of 370 with the horizontal. At the instant when the force is applied the block has a speed of 1.5m/s. if the coefficient of kinetic friction is 0.40, and the block is pulled up 5m, what is the change in the kinetic energy of the block?
- A. 20J
- B. 30J
- C. 40J
- D. 45.5J
Answer, explanation and textbook page: open in the app.
The particles shown in figure below are connected by rectangular rigid nods of negligible mass. The origin of the xy plane is the center of the rectangle. The system rotates in the xy plane about the z axis with an angular speed of 6.00rad/s. what is the rotational kinetic energy of the system? [Figure: A rectangle drawn on a set of x and y axes whose origin, labelled O, is at the centre of the rectangle; the y axis runs vertically up through the middle of the rectangle and the x axis runs horizontally to the right through the middle. A small particle (drawn as a small double circle) sits at each of the four corners. The top-right particle is labelled 2 kg, the bottom-right particle 3 kg, the bottom-left particle 2 kg; the top-left particle carries the label "3" with its unit cut off at the edge of the scan (evidently 3 kg).
- 15.A double-headed vertical arrow at the left of the figure spans the height of the rectangle and is labelled 6 m, with the annotation "Hyp=?" written alongside it. A double-headed horizontal arrow along the bottom of the rectangle spans its width and is labelled 4 m.]
- A. 2574J
- B. 2340J
- C. 1287J
- D. 1170J
Answer, explanation and textbook page: open in the app.
Two blocks are connected by a string of negligible mass passing over a pulley of radius r = 0.2 m and moment of inertia I as shown on figure below. The block on the horizontal frictionless surface is moving with a constant 2.0 m/s2 acceleration = . If the pulley axis is frictionless, the string is inextensible and does not slip on pulley, what should be the moment of inertial of the pulley? [Figure: A shaded block labelled 2 kg rests on a horizontal surface drawn as a line with hatching beneath it. A T 1 horizontal string labelled runs from the right-hand face of the block to a small pulley mounted at the right- T hand edge of the surface.
- 16.From the pulley a vertical string labelled hangs straight down and is attached to the top of a second, unshaded rectangular block labelled 3 kg.] 2 0.40 kgm2 0.80 kgm2
- B. 0.6 kgm2 0.2 kgm2
Answer, explanation and textbook page: open in the app. - 18.Which one of the following statements is not correct about a particle that is in equilibrium?
- A. It can have a velocity different from zero.
- B. Its velocity can be equal to zero.
- C. It can be under the action of more than one force.
- D. It can have an acceleration different from zero.
Answer, explanation and textbook page: open in the app. - 19.Which one of the following laws best describes the behaviour of elastic materials?
- A. Gay Lussae's law
- B. Hook's law
- C. Newton's second law
- D. Newton's law of gravitation
Answer, explanation and textbook page: open in the app. - 20.Two solid spheres made of gold and silver having equal masses are suspended by strings and fully submerged in a tank of water. Given that the density of gold is greater than that if silver, which one of the following statement is true?
- A. The buoyant force on each sphere is the same.
- B. The volume of water displaced by the gold sphere is larger than that of the silver sphere.
- C. The tension in the string supporting each sphere is the same.
- D. The buoyant force on the silver sphere is greater than that on the gold sphere.
Answer, explanation and textbook page: open in the app.
The cross section areas of the small and large pistons of a hydraulic lift shown in figure are and 0.02 m2 , respectively. What is the magnitude of the force that must be applied to the small piston to lift a weight w = 15,000N placed on the larger piston? [Figure: A U-shaped vessel drawn in cross section with thick walls, holding a fluid. Its left limb is narrow and its right limb is wide; each limb is closed by a piston. A vertical arrow pointing downward is drawn inside the left F 1 limb, above the small piston, and is labelled .
- 21.A shaded rectangular block labelled W rests on top of the large piston in the right limb, which sits higher than the small piston.] 3 × 102 2 × 104
- A. N
- B. N 3 × 105 3 × 106
- C. N
- D. N
Answer, explanation and textbook page: open in the app. - 22.An incompressible fluid flows through a horizontal pipe whose diameter varies along its length. The sum of the kinetic energy per unit volume and pressure of the fluid at different section of the pipe would________
- A. depend on the length of the pipe.
- B. Increase as the pipe diameter increases.
- C. Increase as the pipe diameter decreases.
- D. Remain the same as the pipe diameter changes.
Answer, explanation and textbook page: open in the app. - 23.The amount of heat required to raise the temperature of an object of mass m = 1Kg by 1 Kelvin is known as___________
- A. specific heat capacity
- B. heat capacity
- C. expansion coefficient
- D. internal energy
Answer, explanation and textbook page: open in the app. - 24.The first law of thermodynamics takes the form dU = dW. This equation is valid fi the process is________________
- A. isobaric
- B. isochoric
- C. isothermal
- D. adiabatic
Answer, explanation and textbook page: open in the app. - 25.An ideal gas undergoes an isothermal process starting with a pressure of $2 \times 10^5\,\text{pa}$ and a volume of $6\,\text{cm}^3$. Which one of the following might be the pressure and volume of the final state?
- A. $4 \times 10^5\,\text{pa}$ and $4\,\text{cm}^3$
- B. $4 \times 10^5\,\text{pa}$ and $3\,\text{cm}^3$
- C. $5 \times 10^5\,\text{pa}$ and $3\,\text{cm}^3$
- D. $10^5\,\text{pa}$ and $10\,\text{cm}^3$
Answer, explanation and textbook page: open in the app. - 26.The position of a particle moving with simple harmonic motion is given by an expression , where A is the amplitude of the oscillatioin, t is time, is angular frequency, and is the phase constant. If , what will be the sign of the particle's position and velocity at , were T is the period of oscillation?
- A. The position is positive, and the velocity is negative.
- B. The position and velocity are both positive.
- C. The position and velocity are both negative.
- D. The position is negative and the velocity is positive.
Answer, explanation and textbook page: open in the app. - 27.A given minimum point (trough) of a sinusoidal wave is traveling 480 cm long a rope in 12s. If the oscillator that generates the wave completes 48 vibrations in 30s, what is the wave length of the wave?
- A. 25m
- B. 15m
- C. 0.25m
- D. 0.15m
Answer, explanation and textbook page: open in the app. - 28.A wave traveling from a medium of index of refraction toward a medium of index of refraction undergoes n 1 n 2 n 2 n 1 partly transmission and partly reflection. If is greater than which one of the following statements is not correct?
- A. The speed of the wave in the medium with reflective index is smaller than with n 1 n 2
- B. The incident and the reflected waves are in phase.
- C. The angle of reflection is the same as the angle of incidence.
- D. The reflection angle is less than the incidence angle.
Answer, explanation and textbook page: open in the app. - 29.Which one of the following statement is correct?
- A. The electric field strength due to two point charges of equal magnitude and the same sign is zero only at one point on the line joining the two charges.
- B. If a point charge of mass m is released from the rest in uniform electric field, it will move along a line of force with uniform speed.
- C. The variation of the strength of the electric field due to an electric dipole is inversely proportional with the square of the distance from its center of mass.
- D. An electric dipole moment p in a uniform external electric field E is in stable equilibrium if p and E are in opposite directions.
Answer, explanation and textbook page: open in the app. - 30.In a certain region of space, a uniform electric field is directed in the positive x direction. If a particle with negative charge is carried from x = 20cm to x = 60cm, what can we conclude about the electric potential and the electric potential energy of the charge-field system?
- A. The electric potential at x = 20cm is larger than that at x = 60cm.
- B. The electric potential at x = 20cm is the same as that at x = 60cm.
- C. The electric potential energy decrease.
- D. The electric potential energy increase.
Answer, explanation and textbook page: open in the app. - 31.A parallel plate capacitor has a capacitance of $10\,\mu\mathrm{F}$. If the distance between the plates is doubled, keeping all other quantities constant, what is the new capacitance of the capacitor?
- A. $0.2\,\mu\mathrm{F}$
- B. $5\,\mu\mathrm{F}$
- C. $10\,\mu\mathrm{F}$
- D. $20\,\mu\mathrm{F}$
Answer, explanation and textbook page: open in the app. - 32.If several resistors are connected in parallel, the equivalent resistance is
- A. greater than any of the resistances in the group.
- B. is equal to the average resistances of the group.
- C. less than any of the resistances in the group.
- D. equal to the sum of the resistances in the group.
Answer, explanation and textbook page: open in the app. - 33.In aluminium and copper wires with circular cross sections have equal length and equal resistance, then the ratio of the radius of aluminium to that of copper should be the same as that of the________
- A. ratio of the resistivity of aluminium to copper
- B. ratio of the resistivity of copper to aluminium
- C. square root of the ratio of the resistivity of aluminium to copper
- D. square root of the ratio of the resistivity of copper to aluminium
Answer, explanation and textbook page: open in the app.
In the circuit shown below, what is the potential difference between point b and a? [Figure: A circuit made of three horizontal branches joined between a left-hand vertical wire and a right-hand vertical wire. Point a is marked as a node on the left wire where the middle branch meets it; point b is marked as Ω I 3 Ω a node on the right wire where the middle branch meets it. Top branch: a resistor labelled 16 , with a current arrow drawn just beneath it pointing to the LEFT and labelled . Middle branch, running from a to b: a resistor labelled 12 , then a battery labelled 24 V, with a current arrow drawn beneath the resistor pointing to the RIGHT I and labelled .
- 34.Bottom branch: a battery labelled 12 V on the left and a resistor labelled 9 on the right, with a 2 I 1 current arrow drawn beneath the resistor pointing to the LEFT and labelled .]
- A. 19.2V
- B. 24.0V
- C. 13.0V
- D. 12.0V
Answer, explanation and textbook page: open in the app. - 35.An electron moving at a speed of m/s enters a region of uniform magnetic field of magnitude T, direction perpendicular to the field. The path followed by the electron is circular. What is the radius of the circular path?
- A. 0.43cm
- B. 4.3cm
- C. 43cm
- D. 430cm
Answer, explanation and textbook page: open in the app. - 36.If a wire carrying current in the plane of this paper toward the top of the page experiences a magnetic force toward the right edge of the page, what will be the direction of the magnetic field causing this force?
- A. In the plane pf the page and toward the left edge.
- B. In the plane pf the page and toward the bottom edge.
- C. Perpendicular and directed out of the plane of the page.
- D. Perpendicular and directed in to the plane of the page.
Answer, explanation and textbook page: open in the app. - 37.A square flat loop of wire is placed in a uniform magnetic field that is in the y direction. The magnetic flux through the loop is a maximum if the plane of the loop is in the
- A. xy plane
- B. xz plane 45∘
- C. yz plane
- D. inclined with respect to the xy plane
Answer, explanation and textbook page: open in the app. - 38.Which one of the following actions increases the magnetic energy density in the interior of a very long current carrying solenoid?
- A. Increasing the number of turns per unit length of the solenoid.
- B. Increasing the cross section area of the solenoid.
- C. Increasing the length of the solenoid keeping the number of turns per unit length fixed.
- D. Decreasing the cross section area of the solenoid.
Answer, explanation and textbook page: open in the app.