Physics Unit and Measurements Quiz

Unit and Measurements

• The SI unit of power is the Watt.
• 1 Watt is equal to 1 Joule of work done in 1 second.
• Temperature is a fundamental physical quantity and cannot be expressed as a derived quantity in terms of other physical quantities.
• The dimensional formula of stress is the same as pressure; both are represented as 𝑀𝐿−1 𝑇 −2.
• The dimension of strain is 𝑴𝟎 𝑳𝟎 𝑻𝟎.
• The dimension of thermal conductivity is 𝑴𝑳𝑻−𝟑 𝑲−1.
• the dimension of physical quantity: The dimension of a physical quantity are the powers to which the fundamental unit of mass (M), length (L), time (T), temperature (K), electric current (A) have to be raised in order to completely represent that physical quantity.
• Example: Dimension of velocity = 𝐿𝑇 −1 and Dimension of density = 𝑀𝐿−3
• To check if an equation is dimensionally correct, make sure every term in the equation has the same units.
• Calculating Maximum Percentage Error for Density:
  • Density is given by: 𝜌 = 𝑀 / 𝜋𝑟 2 𝑙
  • Take the logarithm of both sides: log 𝜌 = log 𝑀 − log 𝜋 − 2 log 𝑟 − log 𝑙
  • Differentiate both sides: ∆𝜌 / 𝜌 = ∆𝑀 / 𝑀 + 2 ∆𝑟 / 𝑟 + ∆𝑙 / 𝑙
  • For Maximum fractional error of 𝜌, make all signs positive.
• The formula for maximum percentage errors in density is: ∆𝜌 ∆𝑀 ∆𝑟 ∆𝑙 𝜌 = 𝑀 +2 𝑟 + 𝑙

Force and Motion

• Linear Momentum is defined as the product of the mass of the body and its velocity.
• Linear Momentum is measured in kilogram meters per second (kg⋅m/s), and the dimensional formula is 𝑀𝐿𝑇 −1
• Impulse is the product of force and interval of time for which the force acts on a body. Impulse is measured in Newton Seconds (Ns), and the dimensional formula is 𝑀𝐿𝑇 −1
• Impulse is equivalent to the change in linear momentum.
• Impulsive force is a large amount of force acting on a body for a very small interval of time. Impulsive forces are measured in Newtons (N), and the dimensional formula is 𝑀𝐿𝑇 −2
• The principle of conservation of linear momentum states that in a closed system, the total linear momentum is conserved.
• Recoil velocity of a gun can be calculated using the principle of conservation of linear momentum:
  • Let 𝑀 = mass of the gun, 𝑉 = velocity of the gun, 𝑚 = mass of the bullet, 𝑣 = velocity of the bullet
  • Before firing, the total momentum, 𝑀𝑉 + 𝑚𝑣 = 0
  • Therefore, the recoil velocity is: 𝑽 = − 𝒎𝒗 / 𝑀 (the negative sign shows that the direction of the recoil velocity is opposite to the direction of the bullet).
• Newton’s Laws of Motion:
  • First Law: Every body continues in its state of rest or of uniform motion in a straight line, unless it is compelled by some external force to change that state.
  • Second Law: The rate of change of momentum of a body is directly proportional to the force applied on it and the change occurs in the direction of the applied force.
  • Third Law: To every action, there is an equal and opposite reaction.
• Non-conservative force:
  • Work done by a non-conservative force depends on the path taken.
  • A non-conservative force causes a change in mechanical energy.
  • Examples: Air drag and friction.

Test your knowledge on units and measurements in physics with this quiz. Questions cover topics such as SI units, dimensional formulas, and physical quantities. Great for students learning the fundamentals of physics.