Mechanics | Relativity Answers

A firework is placed at rest in the middle of a sheet of ice, and then explodes. The firework breaks into three fragments. One fragment, of mass 0.100 kg, moves off with a velocity of 10 m/s due North. The second, of mass 0.200 kg, moves off with a velocity of 10 m/s due East.
(a) What is the total momentum of the firework (i) just before it explodes, (ii) just after it explodes?
(b)What is the momentum of the third fragment just after the explosion?
(c)The third fragment has a mass of 0.100 kg. What is its velocity just after the explosion?

Parachutists bend their legs and roll with the fall on landing. They do do this to reduce the chance of injury. Explain why this technique means they are less likely to suffer broken bones on hitting the ground.

A bullet of mass 0.01 kg travelling horizontally at 100 m/s penetrates a fixed block of wood and comes to rest in 0.02 s.Calculate (a) the distance of penetration of the bullet into the wood and (b) the average retarding force exerted by the wood on the bullet.

Linear Momentum and Impulse

If Susan had not been wearing her seat belt and not had an air bag, then the windshield would have stopped her head in 0.0015 s. What average force would the windshield have exerted on her?

A block A of mass 5 kg is placed on a rough table. The
coefficient of static and kinetic friction between
surfaces of block and table be 0.4 and 0.3 respectively.
If the force F exerted on the block is 10 N (g = 10 ms–2)
the force of friction between block and table is

A ball kept on a wall is pushed horizontally with
certain velocity and allowed to move under gravity. Such a
motion is two-dimensional motion with ball covering
displacements in both x and y-directions. But both the x & y
direction motions are independent of each other. Hence,
motion in x-direction can be considered as similar to straight
line motion with no acceleration. Motion in y-direction can be
considered as free fall under gravity.
In the figure shown, ball is pushed horizontally from a
height of 19.6 m, with initial velocity as 10 m/s
[Take g = 9.8 m/s2]

1.The horizontal displacement of projectile after 1 sec?
2.The time in which projectile reaches the ground?
3.If there is no energy loss when particle collides at point B on ground, find the maximum
height attained by the particle after it rebounds?
4.The horizontal displacement of projectile when it lands on ground?
5.At what instant vertical speed of particle will be equal to horizontal speed (10 m/s) of particle

In an automatic clothes drier, a hollow cylinder moves the clothes on a vertical circle (radius r = 0.412 m), as the drawing shows. The appliance is designed so that the clothes tumble gently as they dry. This means that when a piece of clothing reaches an angle of θ above the horizontal, it loses contact with the wall of the cylinder and falls onto the clothes below. How many revolutions per second should the cylinder make in order that the clothes lose contact with the wall when θ = 76.0 °?

A satellite has a mass of 6403 kg and is in a circular orbit 4.42 × 105 m above the surface of a planet. The period of the orbit is 2.3 hours. The radius of the planet is 4.73 × 106 m. What would be the true weight of the satellite if it were at rest on the planet’s surface?

A person walks 26 m East and then walks
31 m at an angle 36◦ North of East.
What is the magnitude of the total displacement?

3 grooves AB,AC and AD are made in a circular disk lying in a vertical plane 3 particles B,C and D constrained to move along path AB,AC and AD respectively are released from point A.Particle B reaches point B in time tB,particle C reaches point C in time tC and particle D reaches at point D in time tD.Then which of the following statements is incorrect
tB=tC=tD
tB>tC=tD
tC>tB>tD
tD=tB>tC