Question 59:
(a) What are
(b) State Archimedes’ principle.
(c) When does an object float or sink when placed on the surface of a
Solution :
(a) Those substances which can flow easily are called fluids. All the liquid and gases are fluids, like water, air etc.
(b) Archimedes’ Principle :
When an object is wholly (or partially) immersed in a liquid, it experiences a buoyant force (or upthrust) which is equal to the weight of liquid displaced by the object.
(c) If the buoyant force exerted by the liquid is less than the weight of the object, the object will sink in the liquid. If the buoyant force exerted by the liquid is equal to or greater than the weight of the object, the object will float in the liquid.
Question 60:
(a) How does a boat float in
(b) A piece of steel has a volume of 12 cm^{3}, and a mass of 96 g. What is its density :
(i)
(ii) in kg/
Solution :
(a) A floating boat displaces water equal to its own weight. This displaced water exerts buoyant force to balance the weight of
(b) (i) Mass = 96 g
Volume = 12cm^{3}
Question 61:
An elephant weighing 40,000 N stands on one foot of area 1000 cm^{2} whereas a girl weighing 400 N is standing on one ‘stiletto’ heel of area 1 cm^{2}.
(a) Which of the two, elephant or girl, exerts a larger force on the ground and by how
(b) What pressure is exerted on the ground by the elephant standing on one
(c) What pressure is exerted on the ground by the girl standing on one
(d) Which of the two exerts larger pressure on the
(e) What is the ratio of pressure exerted by the girl to the pressure exerted by the
Solution :
Weight of elephant=40000N
Area of one foot =1000 cm^{2}= 1000 x 10^{4}m^{2}
Weight of girl=400N
Area of heel of girl =1 cm^{2}=1 x 10^{4}m^{2}
(a) Elephant has a larger weight of 40000N, therefore, elephant exerts a larger force on the ground. Elephant exerts a larger force on the ground by 40000N – 400 N=39600N.
(b)Weight of elephant = 40000N
Area of one foot =1000cm^{2}= 1000 x 10^{4}m^{2}
The pressure exerted by
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1. What is the formula for gravitational force between two objects? 
2. How does the mass of an object affect the gravitational force acting on it? 
3. What is the difference between mass and weight? 
4. How does the distance between two objects affect the gravitational force between them? 
5. What is the value of the gravitational constant? 
1 videos228 docs21 tests


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