21. When one body is actually moving over the surface of other body, the friction is known as:
[A] Kinetic friction
[B] Limiting friction
[C] Static friction
[D] Negative friction
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Correct Answer: A [Kinetic friction]
Notes:
When one body is actually moving over the surface of other body, the friction is known as Kinetic friction. It is also known as dynamic friction.
22.What is the product of the mass of the body and its velocity called as?
[A] Force
[B] Linear Momentum
[C] Energy
[D] Power
Hide Answer
Correct Answer: B [Linear Momentum]
Notes:
Linear Momentum is the product of the mass of the body and its velocity. Linear Momentum (p) = mass(m) x velocity(v) p= mv Linear momentum is a vector quantity having the direction same as the direction of velocity of the body
23.What is the average power consumption of a heartbeat in an adult?
[A] 1.2 watt
[B] 112.5 watt
[C] 200 watt
[D] 500 watt
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Correct Answer: A [1.2 watt]
Notes:
Average power consumption by an adult in some of the common processes/activities: 1. Heartbeat – 1.2 watt 2. Sleeping – 75 watt 3. Slow walking – 200 watt 4. Bicycling – 500 watt
24.What should be the angle between force and displacement for maximum work to be done?
[A] 0°
[B] 90°
[C] 180°
[D] 30°
Hide Answer
Correct Answer: A [0°]
Notes:
For maximum work, the angle between force and displacement should be 0°. W = Fs Cos 0° = Fs For zero work, the angle between force and displacement should be 90°. W = Fs Cos 90° = 0
25.What will be the effect on the value of acceleration due to gravity at the poles if the rate of rotation of earth increases?
[A] No effect
[B] it will increase
[C] it will decrease
[D] it will become zero
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Correct Answer: A [No effect]
Notes:
If the rate of rotation of earth increases then the value of acceleration due to gravity decreases at all the places on the surface of earth except at poles.
26.Which of the following has an effect on the value of acceleration due to gravity?
[A] Shape of the earth
[B] Height above the earth surface
[C] Axial rotation of the earth
[D] All of the above
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Correct Answer: D [All of the above]
Notes:
The value of acceleration due to gravity vary due to the following factors : (a) Shape of the earth (b) Height above the earth surface (c) Depth below the earth surface (d) Axial rotation of the earth
27.What is the value of escape velocity for earth?
[A] 9.8 km s-2
[B] 1.6 km s-2
[C] 11.2 km s-2
[D] 7.92 km s-2
Hide Answer
Correct Answer: C [11.2 km s-2]
Notes:
The value of escape velocity is different for different planets. For earth, this value is 11.2 km s-2.
28.What is the height of geo-stationary satellites from the surface of the earth?
[A] 30000 km
[B] 36000 km
[C] 48000 km
[D] 72000 km
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Correct Answer: B [36000 km]
Notes:
The satellite which appears stationary relative to earth is called a geostationary satellite. A geostationary satellite always stays over the same place above the earth. Such a satellite appears stationary due to its zero relative velocity w.r.t. that place on earth. The height of geo-stationary satellites from the surface of the earth is 36000 km.
29.What is the internal restoring force acting per unit area of cross section of the deformed body called?
[A] Strain
[B] Stress
[C] Pressure
[D] Surface Tension
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Correct Answer: B [Stress]
Notes:
Stress is the internal restoring force acting per unit area of cross section of the deformed body. Stress is given by Force/Area.
30.What is the equilibrium distance for Hydrogen atoms?
[A] 0.54 Å
[B] 0.64 Å
[C] 0.74 Å
[D] 0.84 Å
Hide Answer
Correct Answer: C [0.74 Å]
Notes:
When the interatomic force between two atoms is zero, the distance between them is called as normal or equilibrium distance. The equilibrium distance for Hydrogen atoms is 0.74 Å.