KINEMATICS

Name: Assignment III Class: X Subject: Physics

KINEMATICS


I. Choose the correct answer.

1. The final velocity of a freely falling body ( )
(a) 0 (b) v = gt (c) v = 2gh (d) None of these
2. The initial velocity of a freely falling body is ( )
(a) 9.8 ms-1 (b)  (c) 9.8 ms-2 (d) 0
3. Maximum height reached by a body thrown up vertically with an initial velocity u is ( )
(a) u2.2 (b) u2 / 2g (c) 2g/u2 (d) u / g
4. The velocity of a body at its maximum height is ( )
(a) 10 ms-1 (b) 15 ms-1 (c) 0 (d) –10 ms-1
5. The time taken by a body to remain in the air which is moving under the influence of gravity is ( )
(a) 2u /g (b) u/g (c) 2h/g (d) 2h/g
6. The time taken by a body thrown up to reach the maximum height h is called its( )
(a) Time of descent (b) Time of flight (c) Time of ascent (d) None
7. The time taken by a freely falling body to reach the ground is called ( )
(a) Time of descent (b) Time of ascent (c) Time of flight (d) None of these
8. Time for which a body remains in the air is called ( )
(a) Time of flight (b) Time of descent (c) Time of ascent (d) Travelling time
9. For a body if the time of ascent is ‘t’ sec then the time of flight is ( )
(a) t sec (b) 2 t sec (c) 3 t sec (d) 4 t sec
10. The acceleration of a particle projected up at the highest point is ( )
(a) 0 (b) 9.8 cm s-2 (c) 980 cm s-1 (d) 9.8 ms-2

II. Fill in the blanks:

1. When a body moves towards the earth, acceleration due to gravity is taken as __________
2. When a body is projected upwards the acceleration due to gravity is taken as ___________
3. The formula top find the time of ascent is __________
4. Time of ascent is directly proportional to _______________
5. The maximum height reached by a body when it is projected upwards is directly proportional to __________
6. When a body os dropped from a height h, the velocity of the body on reaching the earth is _______________
7. For a body moving under the influence of gravity, time of ascent is equal to __________


8. The bodies projected vertically upwards are subjected to ____________________
9. Bodies falling without any force with a uniform acceleration under the influence of gravity are known as _______________
10. The upward velocity at any point in its flight is the __________ as its downward velocity at that point.

III. 1 Mark questions:

1. Write the equations of motion for a freely falling body
A. V = gt; h = 1/2gt2; v2 = 2gh
2. Write the equations of motion for a body thrown upwards.
A. v = u-gt; h = ut-1/2gt2; v2 = u2-2gh (or) v2 – u2 = -2gh
3. Define the terms a) Time of ascent b) Time of descent c) Time of flight.
A. Time of ascent: The time taken by a body to reach the maximum height when it is thrown up is called time of ascent.
Time of descent: The time taken by a freely falling body to reach the ground is called time of descent
Time of flight: The total time for which the body remains in air is called time of flight.

IV. 2 Marks questions:

1. Obtain a formula to find the maximum height reached by a body when it is projected vertically upwards with a velocity u
2. Derive a formula for the velocity on reaching the ground when a body is dropped from a height h.
3. A Stone is thrown vertically up with an initial velocity of 10 m/sec. Find the maximum height reached and the time of ascent. Take g = 10m/s2
4. A ball is thrown up and attains a maximum height of 80m. Find its initial

V. 4 Marks questions:

1. Show that time of ascent is equal to time of descent (or) Derive the formula to find the time of flight.