Impact of elastic ladies - Basic Level

Impact of elastic ladies - Basic Level

Dear Readers,

Dynamics is the branch of physics developed in classical mechanics concerned with the study of forces and their effects on motion. Isaac Newton was the first to formulate the fundamental physical laws that govern dynamics in classical non-relativistic physics, especially his second law of motion. .

Q1. Two equal perfectly elastic balls impinges directly, then after impact they

•  Are at rest
•  Interchange their velocities
•  Move with the same velocities
•  Move with twice velocities

Solution
Two equal perfectly elastic balls impinges directly, then after impact they Interchange their velocities

Q2.A sphere impinges directly on an equal sphere at rest. If the coefficient of restitution is e, their velocities after the impact are as

•  1:e
•  e:1
•  1+e : 1-e
•  1-e : 1+e

Solution
A sphere impinges directly on an equal sphere at rest. If the coefficient of restitution is e, their velocities after the impact are as 1-e : 1+e

Q3.  A ball is dropped from a height of 22.5 metre on a fixed horizontal plane. If e = 2/5, then it will stop rebounding after

•  5 sec
•  6 sec
•  7 sec
•  8 sec

Solution
it will stop rebounding after 5 sec.

Q4. An elastic ball with coefficient of elasticity 1/2 is dropped from rest at a height h on a smooth floor. The total distance covered by the ball is

•  More than 2h
•  Less than 2h but more than (3/2)h
•  Less than (3/2)h but more that (4/3)h
•  Less then (4/3)h

Solution
The total distance covered by the ball is Less than 2h but more than (3/2)h

Q5.Hailstorm are observed to strike the surface of a frozen lake in a direction making an angle of 30 to the vertical and to rebound at an angle of 60 to the vertical. Assuming the contact to be smooth, the coefficient of restitution is

•  1/3
•  2/3
•  1/√3
•  None of these

Solution
  Assuming the contact to be smooth, the coefficient of restitution is 1/3

Q6. Any heavy elastic ball falls from the ceiling of any room and after rebounding two times reaches the half of the height of ceiling. The coefficient of restitution is

•  (0.50)^1/2
•  (0.50)^1/2
• (0.50)^1/4
•  (0.25)^1/2

Solution
The coefficient of restitution is (0.50)^1/4

Q7.A ball of 1 kg moving with velocity 7 m/sec overtakes and collides with a ball of mass 2 kg moving with velocity 1 m/sec. in the same direction. If e = 3/4, the velocity of the lighter ball after impact is

•  120 m/sec
•   1/2 m/sec
•  1 m/sec
•   0 m/sec

Solution
velocity of the lighter ball after impact is 0 m/sec

Q8.A ball is dropped from a height of 25 dm above a fixed horizontal plane. If it rebounds to a height of 16 dm, then the coefficient of restitution is

•  16/25
•  0.8
•  16g / 25
•  0.8g

Solution
If it rebounds to a height of 16 dm, then the coefficient of restitution is 0.8