Question bank
Practice A-Level CAIE Physics 5 1 Energy Conservation questions by syllabus topic with past-paper context, marks, difficulty and question previews on Eduninja.
Question 1
Question 1(c)
A light meter is used to measure the intensity of light in a classroom. Daylight is incident normally on the sensor of the meter. The sensor has an area of \(2.2 \mathrm{~cm}^{2}\). The reading on the meter is \(950 \mathrm{Wm}^{-2}\). Calculate the power of the daylight incident on the sensor.
power = intensity × area C1 \(=950 \times 2.2 \times 10^{-4}\) C1 \(=0.21 \mathrm{~W}\) A1
Question 1
Question 1(a)
State what is meant by work done.
force × displacement in the direction of the force B1
Question 1
Question 1(b)
Fig. 1.1 shows a turbine that is used to generate electrical power from the wind. The power P available from the wind is given by where L is the length of each blade of the turbine, \(\rho\) is the density of air, v is the wind speed, C is a constant.
Question 1(b)(ii)
The length L of each blade of the turbine is 25.0 m and the density \(\rho\) of air is 1.30 in SI units. The constant C is 0.931 . The efficiency of the turbine is 55 % and the electric power output P is \(3.50 \times 10^{5} \mathrm{~W}\). Calculate the wind speed. wind speed = \(\mathrm{ms}^{-1}\)
power available from wind \(=3.5 \times 10^{5} \times 100 / 55\left(=6.36 \times 10^{5}\right) \quad\) C1 \(v^{3}=3.5 \times 10^{5} \times 100 /\left(55 \times 0.931 \times(25)^{2} \times 1.3\right) \quad\) C1 \(v=9.4 \mathrm{~m} \mathrm{~s}^{-1}\) A1
Question 1
Question 1(b)
A square solar panel with sides of length 1300 mm is shown in Fig. 1.1. Light is incident normally on the solar panel.
Question 1(b)(iii)
The useful power output of the solar panel is 160 W . Calculate the percentage efficiency of the solar panel.
efficiency = useful output power / total input power \[ \begin{aligned} =(160 / 750) \times 100 =21 \% \end{aligned} \] A1
Question 1(b)(iv)
Another square solar panel is placed so that light of the same intensity is incident normally on it. The new panel has shorter sides than the original panel. The new panel has the same power output as the original panel. State and explain whether the efficiency of the new panel is greater than, less than or the same as the efficiency of the original panel.
area (of the new panel) is less B1 input power (of the new panel) is less (than the input power of the original panel) (as intensity is constant) B1 (useful power output is unchanged so) efficiency is greater (than the original panel) B1
Question 1
Question 1(a)
Question 1(a)(i)
Define power.
work done per unit time B1
Question 1
Question 1(b)
Fig. 1.1 shows the path of a comet of mass \(2.20 \times 10^{14} \mathrm{~kg}\) as it passes around a star of mass \(1.99 \times 10^{30} \mathrm{~kg}\). At point X , the comet is \(8.44 \times 10^{11} \mathrm{~m}\) from the centre of the star and is moving at a speed of \(34.1 \mathrm{~km} \mathrm{~s}^{-1}\). At point Y , the comet passes its point of closest approach to the star. At this point, the comet is a distance of \(6.38 \times 10^{10} \mathrm{~m}\) from the centre of the star. Both the comet and the star can be considered as point masses at their centres.
Question 1(b)(iii)
Use your answer in (b)(i) to determine the speed, in \(\mathrm{km} \mathrm{s}^{-1}\), of the comet at point Y . speed = \(\mathrm{km} \mathrm{s}^{-1}\)
\(\Delta E_{\mathrm{P}}=1 / 2 m\left(v_{2}{ }^{2}-v_{1}{ }^{2}\right)\) C1 \(4.23 \times 10^{23}=1 / 2 \times 2.20 \times 10^{14} \times\left(v^{2}-34100^{2}\right)\) C1 \(v\left(=70800 \mathrm{~m} \mathrm{~s}^{-1}\right)=70.8 \mathrm{~km} \mathrm{~s}^{-1}\) A1
Question 3
A1.5 V cell supplies 0.20 A to a lamp for seven hours before the lamp goes out. What is a sensible estimate for the initial chemical energy content of the cell? \(1 \times 10^{2} \mathrm{~J}\) \(1 \times 10^{4} \mathrm{~J}\) \(1 \times 10^{6} \mathrm{~J}\) \(1 \times 10^{8} \mathrm{~J}\)
B
Question 3
An ion is accelerated by a series of electrodes in a vacuum. A graph of the power supplied to the ion is plotted against time. What is represented by the area under the graph between two times? the change in kinetic energy of the ion the average force on the ion the change in momentum of the ion the change in velocity of the ion
A
Question 2
An archer releases an arrow towards a target at a velocity of \(65.0 \mathrm{~ms}^{-1}\) at an angle of \(4.30^{\circ}\) above the horizontal, as shown in Fig. 2.1. When released, the tip of the arrow is a horizontal distance of 70.0 m from the target and 1.66 m above the horizontal ground. The arrow hits the centre of the target. Assume that air resistance is negligible and that all the mass of the arrow is at its tip.
Question 2(c)
By considering energy changes, state and explain how the final kinetic energy of the arrow as it hits the target compares with its initial kinetic energy immediately after release. A numerical calculation is not required.
GPE has decreased M1 (total energy conserved so) KE has increased A1
Question 2
Question 2(a)
Define
Question 2(a)(ii)
work done.
work done is the product of the force and the distance moved in the direction of the force
Question 2(b)
A force F acts on a mass m along a straight line for a distance s. The acceleration of the mass is a and the speed changes from an initial speed u to a final speed v.
Question 2(b)(i)
State the work W done by F.
W=F s or W=m a s or \(W=m\left(v^{2}-u^{2}\right) / 2\) or W= force × distance s
Question 2(c)
A resultant force of 3800 N causes a car of mass of 1500 kg to accelerate from an initial speed of \(15 \mathrm{~ms}^{-1}\) to a final speed of \(30 \mathrm{~ms}^{-1}\).
Question 2(c)(ii)
The same force is used to change the speed of the car from \(30 \mathrm{~ms}^{-1}\) to \(45 \mathrm{~ms}^{-1}\). Explain why the distance moved is not the same as that calculated in (i).
the change in kinetic energy is greater or the work done by the force has to be greater, hence distance is greater (for same force) allow: same acceleration, same time, so greater average speed and greater distance