Question

Một vật có khối lượng 2 kg rơi tự do xuống đất trong khoảng thời gian 0,5 s. Độ biến thiên động lượng của vật trong khoảng thời gian đó là bao nhiêu ? Cho g = 10 m/s2.

Answer 1

Answer: The change in momentum is +20 kg.m/s

Step-by-step explanation:

To calculate the final velocity of object, we use the first equation of motion:

`v=u+at`

where,

v = final velocity

u = initial velocity = 0 m/s

a = acceleration =
`10m/s^2`

t = time = 0.5 s

Putting values in above equation, we get:

`v=0+(10* 0.5)\\\\v=5m/s`

Momentum is defined as the product of the mass and velocity of an object. It is given by the equation:

`p=mv`

where,

p = momentum

m = mass of object = 2 kg

Let the upward velocity be positive and the downward velocity be negative

When the object is dropped, the velocity is downward

v = -5m/s

Initial momentum =
`2kg* (-5m/s)=-10kg.m/s`

When the object is bounced back, the velocity is upward

v = +5m/s

Final momentum =
`2kg* (+5m/s)=10kg.m/s`

Change in momentum = Final - Inital

Change in momentum = [10 - (-10)] = +20 kg.m/s

Hence, the change in momentum is +20 kg.m/s