IRSA IMPORTANT QUESTIONS

Question 1

What does Newton’s first law of motion state? What is it also known as?

Answer 1

Newton’s first law states that an object at rest will remain at rest while an object moving will continue to do so unless acted upon by an external force. First law of motion is also called law of inertia

Question 2

Define and list the equation for angular acceleration?

Answer 2

Angular acceleration acts towards the centre of the circle and is given by a_R=𝒗^𝟐/r

Question 3

What direction is force, acceleration and velocity acting in circular motion?

Answer 3

In circular motion, centripetal acceleration and velocity are always at Right angles to one another.

Question 4

What is amplitude?

Answer 4

Amplitude is the maximum displacement from the equilibrium position of an oscillating object.

Question 5

What does the first law of thermodynamics state?

Answer 5

Energy cannot be created or destroyed, only transferred or converted from one form to another.

Question 5

What is a magnetic flux? What does it represent in terms of magnetic fields?

Answer 5

Magnetic flux is ameasure of the flow of a magnetic field through a given area

The number of magnetic field lines passing through a surface.

Question 6

What does Gauss’s Law for magnetism state?

Answer 6

the magnetic flux through a closed surface is always zero

Question 7

What device is used to measure electromagnetic induction?

Answer 7

Galvanometer

Question 8

How does AC differ from DC

Answer 8

AC continuously changes direction, while DC flows steadily in one direction. AC is categorized by a waveform that alternates, whereas DC has a constant, unidirectional flow.

Question 9

What is the frequency of AC in most households?

Answer 9

In most households, the AC frequency is 60 hertz (Hz) in North America and 50 Hz in many other parts of the world. It represents the number of complete cycles per second

Question 10

How is the strength of a gravitational field determined?

Answer 10

The strength of a gravitational field is determined by the mass of the object creating the field. The greater the mass, the stronger the gravitational field.

Question 11

How does an electromagnet work?

Answer 11

An electromagnet is a coil of wire with an electric current flowing through it. It generates a magnetic field when the current flows, and you can control the strength and direction of the field by adjusting the current.

Question 12

What is the unit of measurement for electric field strength?

Answer 12

The unit of measurement for electric field strength is volts per meter (V/m).

Question 13

What is the ideal gas law?
State the equation.

Answer 13

The ideal gas law is an equation that describes the behaviour of an ideal gas. It is typically written as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature in Kelvin.

Question 14

How does an increase in pressure affect the volume of a gas, assuming constant temperature and moles?

Answer 14

According to Boyle’s law, an increase in pressure, with constant temperature and moles, will result in a decrease in the volume of a gas, and vice versa.

Question 15

What is centripetal acceleration?

Answer 15

Centripetal acceleration is the acceleration directed toward the center of a circular path that keeps an object in circular motion.

Question 16

Define simple harmonic motion

Answer 16

Simple Harmonic Motion (SHM) is a type of periodic motion in which an object oscillates back and forth around a central point, or equilibrium position, with a restoring force proportional to its displacement. In simpler terms, it is a repetitive, to-and-fro movement.

Question 17

What is the Second law of thermodynamics?

Answer 17

The Second Law of Thermodynamics states that the total entropy (a measure of disorder or randomness) of an isolated system always increases over time.

Question 18

What happens to the kinetic energy of a particle moving in a circle with uniform speed?

Answer 18

The kinetic energy of the particle is constant.

Question 19

Two identical uniform spheres each of radius R are placed in contact. The gravitational force between them is F. The spheres are now separated until the force of attraction is F/9. What is the distance between the surfaces of the spheres after they have been separated?

Answer 19

4R

Question 20

(c) Describe one way in which the motion of the molecules of air inside the bicycle tyre is similar and one way in which it is different at the two temperatures.

Answer 20

Similar - rapid random motion, range of speeds

Different - mean kinetic energy, root mean square speed, Frequency of collisions

Question 21

What is angular speed (w)

Answer 21

Angular speed is the rate at which an object rotates around a specific point. It can be calculated using the formula

ω=2π/T
Where: ω = angular speed (in radians per second)
T = time taken to complete one full revolution (in seconds)

Question 22

What is centripetal acceleration?

Answer 22

Centripetal Acceleration (ac): Centripetal acceleration is the acceleration experienced by an object moving in a circular path and can be calculated using the formula: ac=𝑉^2 /r

Question 23

To celebrate the Millennium in the year 2000, a footbridge was constructed across the river Thames in London. After the bridge was opened to the public, it was discovered that the structure could easily be set into oscillation when large numbers of pedestrians were walking across it.
(a) what name is given to this kind of physical phenomenon, when caused by a periodic driving force?
(b) Under what condition would this phenomenon become particularly hazardous? Explain your answer.
c) Suggest two measures which engineers might adopt in order to reduce the size of oscillations of the bridge.

Answer 23

a) Name of the Phenomenon:
The kind of physical phenomenon where a structure is set into oscillation by a periodic driving force is known as “resonance.”
(b) Hazardous Conditions:
This phenomenon becomes particularly hazardous when the frequency of the periodic driving force matches the natural frequency of the structure. In such a scenario, resonance amplifies the oscillations, leading to larger and more destructive vibrations. If the bridge is subjected to forces at its natural frequency, it can result in significant structural vibrations and potential damage
) Measures to Reduce Oscillations:
Engineers can adopt the following measures to reduce the size of oscillations of the bridge:
1. Adjusting the Natural Frequency:
Modify the structural properties of the bridge to change its natural frequency. This could involve adjusting the stiffness or mass distribution to avoid resonance with common frequencies generated by pedestrian movement.
2. Damping Systems:
Implement damping systems on the bridge to dissipate energy and reduce oscillations. Damping mechanisms, such as shock absorbers or tuned mass dampers, can be strategically installed to absorb and dissipate the vibrational energy, preventing excessive oscillations.
These measures aim to mitigate the resonance effect and enhance the stability and safety of the bridge, especially during periods of high pedestrian traffic.

Question 24

A small body of mass rests on a horizontal turntable at a distance r from the centre. If the maximum frictional force between the body and the turntable is 𝑚𝑔/2, what is the angular speed at which the body starts to slip?

Answer 24

Root g/2r