Physics Section 4

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• 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.