Showing posts with label Momentum. Show all posts
Showing posts with label Momentum. Show all posts

2020-05-15

Linear momentum collision problem calculations 2

Questions 

1.     A toy truck with a mass of 3 kg was moving at 3 ms-1 and hit with another toy truck of 1 kg and was moving with a velocity of 1 ms-1, in the opposite direction. After collision, both trucks moved together in the same direction, calculate the common velocity of the two objects after collision.

 

m1u1 + m2u2 =  (m1+ m2)v

            (3)(3) + (1)(-1) = (3+1)v

            9 – 1 = 4v

            v = 2 ms-1

 

2.     A hunter shot a 100g bullet from a 1.5kg gun. If the bullet travelled 200 ms-1 after being triggered, what is the backward jerk of the gun. (Think final backward velocity of the gun).

 

Total initial momentum = Total final momentum = 0

m1u1 + m2u2 = 0

1.5(v) + 0.1(200) = 0 ß make sure to convert 100g to kg

1.5v +20 = 0

v = - 13.3 ms-1   ß Value is negative because gun moved in opposite direction

 

3.     A trolley of mass 2 kg was in a stationary condition, before a 5 g sticky plasticine was thrown into it with a velocity of 500 ms-1. After hitting the trolley, the plasticine sticks into it. Calculate the final velocity of both the trolley and plasticine?

Use the classic formula of momentum conservation

m1u1 + m2u2 = m1v1 + m2v2

0.005 (500) + 2 (0) = (0.005+ 2)v

2.5 = 2.005v

 v = 1.245 ms-1        

 

2007-10-22

Analysing Momentum

The momentum of an object is the product of its mass and its velocity.

p = m X v

The principles of conservation of liner momentum states that the total linear momentum of a closed system is constant.

The linear momentum before and after a collision is conserved if there is no external force acting on it.

Elastic collision: linear momentum, kinetic energy and total energy are conserved.

Inelastic collision: only linear momentum and total energy are conserved and there is a loss in kinetic energy.

In an EXPLOSION, where two objects move in opposite directions, the total linear momentum before and after the explosion is zero.

The acceleration of a rocket leaving the earth increases because:
a) its mass is decreasing.
b) air resistance is decreasing.
c) gravitational pull is decreasing.