## Physics Section 4

- When encountering an atom, an alpha particle knocks out electrons.
- The path of an alpha particle is zig-zag or erratic.
- γ-rays are suitable for treating infections inside the body.
- Cobalt-60 is used to treat various types of cancer.
- Surgical instruments can be sterilized by exposing them to γ-rays.
- Alpha particles carry a charge of plus two.
- An alpha particle ionizes an atom through electrostatic repulsion.
- TVs and microwave ovens emit X-rays.
- An alpha particle loses most of its energy in a single encounter.
- Strontium-90 is used as an α-particle source.
- Gamma rays are used to sterilize surgical equipment due to their high penetration.
- Beta particles ionize an atom due to electrostatic force of repulsion.
- Alpha particles possess greater penetration power due to smaller ionization power.
- Pair production cannot occur in a vacuum due to momentum not being conserved.
- Pair production can take place with gamma rays.
- A linear accelerator is a device for producing high-velocity nuclei.
- Lead is a better shield against gamma rays.
- The maximum safe limit dose for nuclear power station workers is 5 rem per week.
- Gamma rays are used for treating skin in patients.
- Physics plays an important role in technology and engineering development.
- Geology is not a branch of physical sciences.
- Physical quantities are divided into two categories.
- SI units have three types of units.
- In scientific notation, numbers are expressed in powers of ten.
- 1024 can be written in scientific notation as 1.024×10³.
- The prefix “deca” represents 10 raised to power 1.
- Errors in measurements may occur due to various reasons.
- Uncertainty in measurements can be reduced by taking the mean of several measurements.
- Random errors can be reduced by taking the mean of several measurements.
- Significant figures in a measurement include all accurately known digits and the first doubtful digit.
- A digit zero in a measurement may or may not be significant.
- The number of significant figures in 0.0173 is 3.
- Smaller least count instruments result in more precise measurements.
- The dimension of force is MLT⁻².
- The dimension of pressure is ML⁻¹T⁻².
- Dimensional analysis is helpful for deriving formulas and checking homogeneity of equations.
- The equation S = Vt² is not dimensionally correct.
- The SI unit of the coefficient of viscosity is kg m⁻¹s⁻¹.
- A correct measurement of a needle’s length is 0.214 m.
- Uncertainty in measurements depends on the instrument’s least count.
- The solid angle unit is steradian.
- An ideal standard of measurement is accessible and invariable.
- Total uncertainty in a result is the sum of absolute uncertainties.
- Giga is the highest power multiple.
- One pico stands for 10 raised to power -12.
- The unit of G is N m² kg⁻².
- The correct representation for the unit of pressure is newton/meter².
- The correct record of three measurements of a needle’s length is (iii) 0.214 m.
- Absolute uncertainty in a measurement depends on limitations of an instrument and natural variation.
- The number of main frontiers of fundamental science is 3.
- One light year is equal to approximately 9.5 x 10¹⁵ meters.
- A dimensionally correct equation is S = Vit + 1/2at².
- The error in measurement known as zero error is a systematic error.
- Uncertainty in a measurement may occur due to limitations of an instrument, natural variation, and technique.
- The number of significant figures in 5.400 is none.
- To reduce uncertainty in a timing experiment, highly precise instruments and counting vibrations can be used.
- The number of significant figures in the length of a bar measured by a meter rod is 4.
- The number 76.85 rounded off to two significant figures is 77.
- The representation of prefixes should be consistent, such as 1 mm or 10 km.
- The rotational kinetic energy of a hoop is equal to its translational kinetic energy.
- A hoop has twice the rotational kinetic energy of a disc with the same mass and radius.
- The critical speed of an artificial satellite is 7.9 km/s.
- A geostationary satellite completes one rotation around the Earth in 24 hours.
- The radius of a geostationary orbit is approximately 42,000 km.
- Gravitational interaction is possible between material objects and electromagnetic radiation.
- One radian is equal to approximately 57.3 degrees.
- The angular speed of the minute hand of a clock is π/30 radians per minute.
- In SHM, the maximum displacement from the mean position is called the amplitude.
- A body with high momentum is difficult to stop compared to a body with low momentum.
- The change in momentum of an object is equal to the impulse acting on it.
- The momentum of an isolated system is conserved.
- An astronaut in space throws a wrench; the astronaut will move in the opposite direction.
- An object at rest can have momentum if it has mass.
- The acceleration of an object is directly proportional to the net force applied to it.
- The SI unit of force is the newton.
- An object will remain at rest or in uniform motion unless acted upon by a net external force.
- The acceleration due to gravity is approximately 9.8 m/s².
- Friction always opposes the motion of objects.
- In circular motion, centripetal force is directed outward from the center.
- The gravitational force between two objects increases as the distance between them decreases.
- The weight of an object is the force with which it is attracted towards the center of the Earth.
- A force of 10 N applied to a 2 kg object will result in an acceleration of 5 m/s².
- An object with a mass of 5 kg is accelerated at 2 m/s². The net force applied to it is 10 N.
- Newton’s First Law is also known as the Law of Inertia.
- Momentum is the product of an object’s mass and velocity.
- The rate of change of momentum is equal to the net external force applied to an object.
- Impulse is the product of force and time over which it acts.
- The SI unit of impulse is the newton-second.
- Newton’s Third Law states that action and reaction are equal in magnitude and opposite in direction.
- A solid cube will sink in a liquid if its density is greater than the density of the liquid.
- The buoyant force acting on an object in a fluid is equal to the weight of the fluid displaced by the object.
- The pressure in a fluid at a specific depth is the same in all directions.
- Pascal’s Law states that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid.
- A hydraulic press works based on Pascal’s Law.
- The mechanical advantage of a machine is the ratio of output force to input force.
- A first-class lever has the fulcrum between the input and output forces.
- The efficiency of a machine is the ratio of useful work output to total work input.
- The ideal mechanical advantage of a machine is calculated by dividing the input distance by the output distance.
- A block and tackle system is an example of a machine that increases the mechanical advantage.
- Gears are an example of a machine that can change the direction of force.