Question:
A car falls off a ledge and drops to the ground in 0.5 s.Let g = (for simplifying the calculations).
(i) What is its speed on striking the ground ?
(ii) What is its average speed during 0.5 s ?
(iii) How high is the ledge from the ground ?
Answer:
(i) 5 m/s (ii) 2.5 m/s (iii) 1.25 m
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
A particle is dropped from a tower 180 m high.How long does it take to reach the ground ? What is the velocity when it touches the ground ? Take g =
Q 3.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 4.
A boy on a clif£ 49 m high drops a stone.One second later,he throws a second stone after the first.They both hit the ground at the same time. With what speed did he throw the second stone ?
Q 5.
Why do sewing needles and all pins have a sharp pointed tip?
Q 6.
What is the value of ‘g’ at the centre of Earth ?
Q 7.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 8.
Which force is responsible for tides in the ocean at night ?
Q 9.
Two stones A and B are dropped from a multistoried building. A is dropped from 100 m and after some time B is dropped from 50 m height. Both of them reach the earth at the same time. Will they have equal velocity while reaching the ground ? Calculate and find out the answer (take g =10 m/s
2).
Q 10.
What do you mean by acceleration due to gravity ?
Q 11.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 12.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 13.
The mass of Earth is
kg and that of moon is
kg. If the distance between the Earth and the Moon is
km, calculate the force exerted by Earth on the Moon. Given G =
.
Q 14.
Who measured the value of G first time, experimentally?
Q 15.
At what height above the surface of the earth, the value of 'g' becomes 64% of its value at the surface of the earth. Take radius of the earth = 6400 km.
Q 16.
Suppose a planet exists whose mass and radius both,are half those of Earth.Calculate the acceleration due to gravity on the surface of this planet.
Q 17.
What do we call the gravitational force between the Earth and an object ?
Q 18.
What are the differences between the mass of an object and its weight?
Q 19.
Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?
Q 20.
What is the acceleration of free fall ?
Q 21.
What is the weight of a body of mass 1 kg on Earth ?
Q 22.
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Q 23.
Fill in the blanks :
Kepler's Law of ______ states that a line that connects a planet to the Sun sweeps out equal ______ in the plane of the planet's orbit in _____time intervals.
Q 24.
Why is G called the Universal Constant?
Q 25.
Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10
24 kg and of the Sun = 2 × 10
30 kg. The average distance between the two is 1.5 × 10
11 m.
Q 26.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 28.
A cuboid room has dimensions 50m x 15m x 3.5m. What is the mass of the air enclosed in the room if the density of air = 1.30 kg/m
3.
Q 29.
Calculate the force of gravitation between two objects of masses 80 kg and 1200 kg kept at a distance of 10 m from eachother.Given, G =
/
.
Q 30.
State the universal law of gravitation.
Q 31.
What is the importance of universal law of gravitation ?
Q 32.
Who explained the motion of planets around the Sun ?
Q 33.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 34.
Fill in the blanks :
The force which keeps the object moving in a circular path is called _____ force. It always acts towards the _____.
Q 35.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 36.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 38.
Why will a sheet of paper fall slower than one that is crumpled into a ball?
Q 39.
As you climb up a mountain, your ears “pop” because of the changes in atmospheric pressure. In which direction, outward or inward, does your eardrum move when you climb up?
Q 40.
Loaded test-tube placed in pure milk sinks to a certain mark (M). Now some water is mixed with the milk. Will the test tube sink more or less? Explain.
Q 41.
An object is thrown vertically upwards and rises to a height of 10 m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point.
Q 42.
Gravitational force acts on all objects in proportion to their masses.Why then,a heavy object does not fall faster than a light object ?
Q 43.
Who gave three laws of planetary motion ?
Q 44.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 45.
What is the SI unit of mass ?
Q 46.
What is the SI unit of weight ?
Q 47.
Can a body have mass but no weight ?
Q 48.
Can a body have weight but no mass ?
Q 49.
State Kepler’s Laws of planetary motion.
Q 50.
Distinguish between mass and weight.
