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Introduction to Physics — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsIntroduction to Physics4 Marks
Question
A dimensionless quantity:
  1. Never has a unit.
  2. Always has a unit
  3. May have a unit.
  4. Does not exist.
✓

Answer

  1. May have a unit.
Explanation:

Dimensionless quantities may have units.

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Certain collisions are referred to as elastic collisions. Elastic collisions are collisions in which both momentum and kinetic energy are conserved. The total system kinetic energy before the collision equals the total system kinetic energy after the collision. If total kinetic energy is not conserved, then the collision is referred to as an inelastic collision.
The coefficient of restitution, denoted by (e), is the measure of degree elasticity of collision. It is defined as the ratio of the final to inital relative speed between two objects after they collide. It normally ranges from 0 to 1 where 1 would be a perfectly elastic collision. A perfectly inelastic collision has a coefficient of 0 . In real life most of the collisions are neither perfectly elastic nor perfectly inealstic and $0< e <1$.

1. The following are the data of a collision between a truck and a car.
Mass of the car $=1000 kg$
Mass of the truck $=3000 kg$
Mass of the truck Before collision:
Speed of the car $=20 m / s$
Momentum of the car $=20000 kg m / s$
Speed of the truck $=20 m / s$
Momentum of the truck $=60000 kg m / s$
After collision:
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Momentum of the car $=40000 kg m / s$ in the opposite direction
Speed of the truck $=0$
Momentum of the truck $=0$
The collision is
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(b) Elastic since momentum is conserved
(c) Inelastic since kinetic energy is conserved
(d) Elastic since kinetic energy is conserved
2. The coefficient of restitution is the measure of
(a) Malleability of a substance    (b) Conductivity of a substance
(c) degree of elasticity of collision    (d) Elasticity of a substance
3. Coefficient of restitution is defined as
(a) 
Image
(b) Relative velocity after collision x relative velocity before collision
(c) Relative velocity after collision + relative velocity before collision
(d) 
Image
OR
In real life most of the collisions are
(a) Range of coefficient of restitution is 0 < e < 1
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(c) neither perfectly elastic nor perfectly inelastic
(d) perfectly inelastic
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(a) $+1,-1$    (b) 0,1    (c) $0,-1$    (d) 1,0
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  2. The motion is along a straight line about the mean position.
  3. The oscillations are responsible for the energy conversion.
  4. The acceleration of the particle is directed towards the extreme position.
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  2. $\frac{\text{d}^2\text{x}}{\text{dt}^2}=-\omega^2\text{t}$
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  2. Area
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  3. Both large as well as small oscillations of spring
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  1. Give expression for restoring force in spring while performing small SHM oscillations.
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  3. Explain oscillations due to spring.
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 The force producing a resistance to the oscillation is called damping force.
  1. particle oscillating under force $\overrightarrow{\text{F}}=-\text{k}\overrightarrow{\text{x}}-\text{b}\overrightarrow{\text{v}}$ is a (k and b are constants)
  1. Simple harmonic oscillator
  2. Linear oscillator
  3. Damped oscillator
  4. Forced oscillator
  1. Which of the following displacement-time graphs represent damped harmonic oscillation?
  1. In case of a force vibration, the resonance wave becomes very sharp when the
  1. Applied periodic force is small
  2. Quality factor is small
  3. Damping force is small
  4. Restoring force is small
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  2. $kg^2s$
  3. $kg m/s$
  4. $kg/s$
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