2018 - WAEC Physics Past Questions and Answers - page 4
Two objects P and Q of masses 100kg and 20kg respectively are 1.2m apart on a horizontal surface. Calculate the net gravitational force acting on Q. \([G= 6.67 \times 10^{-11} Nm^{2}kg^{-2}]\)
\(1.11\times 10^{-7} N\) towards P
\(1.11\times 10^{-7} N\) towards Q
\(9.26\times 10^{-8} N\) towards P
\(9.26\times 10^{-8} N\) towards Q
\(F= \frac{Gm_{1}m_{2}}{r^{2}}\)
\(m_{1} = 100kg\)
\(m_{2} = 20kg; r =1.2m\)
\(G= 6.67\times 10^{-11}\)
\(F = \frac{6.67\times 10^{-11}\times 100\times 20}{(1.2)^{2}} = 9.26\times 10^{-8}\)
The acceleration of an object is inversely proportional to its mass. Hence, the lighter the object the faster it can move... the force will act in the direction of Q.
The primary of a transformer has 100 turns and its secondary has 200 turns. If the voltage at the primary is 100V, determine the voltage at the secondary.
50V
100V
200V
400V
The equation of ideal transformer:
\(\frac{V_{s}}{V_{p}} = \frac{N_{s}}{N_{p}} = \frac{I_{p}}{I_{s}}\)
where \(V_{s}\) and \(V_{p}\) are the voltages applied to the secondary and the primary respectively
\(N_{s}\) and \(N_{p}\) are the number of turns on the secondary and primary coils respectively
\(I_{p}\) and \(I_{s}\) are the currents flowing in the primary and secondary coils respectively.
\(\frac{V_{s}}{100} = \frac{200}{100}\)
\(V_{s} = \frac{200\times 100}{100} = 200V\)
In the diagram illustrated a block of mass M is at rest on a plane inclined at an angle \(\theta\) to the horizontal. As \(\theta\) increases, the velocity ratio of the plane
The velocity ratio and therefore, the mechanical advantage of an inclined plane system increases as \(\theta\) decreases and vice-versa.
When the speed of a car is halved, its kinetic energy is
doubled
quartered
halved
quadrupled
Given \(K_{1}\) = \(\frac{mv^{2}}{2}\).
When v is halved, we have
\(K_{2}\) = \(\frac{m\times (\frac{v}{2})^{2}}{2}\)
= \(\frac{K_{1}}{4}\), which is a quater
A wire of length 400cm is stretched between two fixed points. When plucked, its fundamental frequency is 150Hz. Calculate the speed of the wave produced.
The fundamental frequency \((f_{0})\) = \(\frac{v}{2l}\)
\(f_{0} = 150Hz; l =400cm = 4m\)
\(150 = \frac{v}{2\times 4}\)
\(v = 150 \times 8 = 1200ms^{-1}\)
The diagram above illustrates a waveform. Determine the number of wavelengths in it
A resistor with fixed resistance value is called a
Which of the following statements is not an advantage of an alkaline accumulator?
The diagram above illustrates the wire connections to a three-pin plug. The wires P, Q and R respectively are:
Which of the following statements about parallel plate capacitors is/are correct?
I. Capacitance of the capacitor is inversely proportional to the distance between the plates
II. Capacitors can filter a.c signals from d.c
III. Capacitors can store charges
I only
I and II only
II and III only
I, II and III
Capacitors pass AC but block DC signals (when charged up to the applied DC voltage). They are often used to
- separate the AC and DC components of a signal
- store energy