If No is the original mass of the substance of half-life period t1/2 = 5 years, then the amount of substance left after 15 years is:
A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m which applying the force and the ball goes upto 2 m height further, find the magnitude of the force. Consider g = 10 m/s2
A block rests on a rough inclined plane making an angle of 30° with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is
A marble block of mass 2 kg lying on ice when given a velocity of 6 m/s is stopped by friction in 10 s. Then the coefficient of friction is
A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads 49 N, when the lift is stationary. If the lift moves downward with an acceleration of 5 m/s2, the reading of the spring balance will be
Three identical blocks of masses m = 2 kg are drawn by a force F = 10.2 N with an acceleration of 0.6 ms–2 on a frictionless surface,then what is the tension (in N) in the string between the blocks B and C
A light string passing over a smooth light pulley connects two blocks of masses m1 and m2 (vertically). If the acceleration of the system is g/8, then the ratio of the masses is
One end of a massless rope, which passes over P a massless and frictionless pulley P is C tied to a hook C while the other end is free.
Maximum tension that the rope can bear is 960 N. With what value of maximum safe acceleration (in ms–2) can a man of 60 kg climb on the rope?
When forces F1, F2, F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular, then the particle remains stationary. If the force F1 is now removed then the acceleration of the particle is
When forces F1, F2, F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular, then the particle remains stationary. If the force F1 is now removed then the acceleration of the particle is
A lift is moving down with acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively
The kinetic energy needed to project a body of mass m from the earth surface (radius R) to infinity is
Energy required to move a body of mass m from an orbit of radius 2R to 3R is
If suddenly the gravitational force of attraction between Earth and a satellite revolving around it becomes zero, then the satellite will
If g is the acceleration due to gravity on the earth’s surface, the gain in the potential energy of an object of mass m raised from the surface of the earth to a height equal to the radius R of the earth is
The time period of an earth satellite in circular orbit is independent of
A satellite of mass m revolves around the earth of radius R at a height x from its surface. If g is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is
The escape velocity for a body projected vertically upwards from the surface of earth is 11 km/s. If the body is projected at an angle of 45° with the vertical, the escape velocity will be
Two spherical bodies of mass M and 5M and radii R and 2R respectively are released in free space with initial separation between their centres equal to 12R. If they attract each other due to gravitational force only, then the distance covered by the smaller body just before collision is
The time period of a satellite of earth is 5 hour. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time period will become
The escape velocity of a body depends upon mass as
Describe briefly Ultraviolet B
Describe briefly Catalytic converter
Describe briefly Greenhouse gases
What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Describe briefly Municipal solid wastes
Describe briefly Defunct ships and e-wastes
Describe briefly Radioactive wastes
What measures, as an individual, you would take to reduce environmental pollution?
Discuss the role of women and communities in protection and conservation of forests.
Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment
Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
List all the wastes that you generate, at home, school or during your Trips to other places, could you very easily reduce? Which would be Difficult or rather impossible to reduce?
What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
What measures, as an individual, you would take to reduce environmental pollution?
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
What are sacred groves? What is their role in conservation?
How is biodiversity important for ecosystem functioning?
What are the major causes of species losses in a geographical region?
What is the significance of the slope of regression in a species − area relationship?
Give three hypotheses for explaining why tropics show greatest levels of species richness.
How do ecologists estimate the total number of species present in the world?
Name the three important components of biodiversity
Outline salient features of carbon cycling in an ecosystem
Write important features of a sedimentary cycle in an ecosystem.
Give an account of energy flow in an ecosystem.
Define decomposition and describe the processes and products of decomposition.
What is primary productivity? Give brief description of factors that affect primary
productivity.