Here we apply conservation of linear momentum. The momentum of the truck with cargo and without cargo remains constant. That is,
.
Here are initial mass and velocity.
are final mass and velocity. Here
and
.
The velocity of the truck be after its cargo is taken off is
Answer:
(a) 89 m/s
(b) 11000 N
Explanation:
Note that answers are given to 2 significant figures which is what we have in the values in the question.
(a) Speed is given by the ratio of distance to time. In the question, the time given was the time it took the pulse to travel the length of the cable twice. Thus, the distance travelled is twice the length of the cable.
(b) The tension, , is given by
where is the speed,
is the tension and
is the mass per unit length.
Hence,
To determine , we need to know the mass of the cable. We use the density formula:
where is the mass and
is the volume.
If the length is denoted by , then
The density of steel = 8050 kg/m3
The cable is approximately a cylinder with diameter 1.5 cm and length or height of 620 m. Its volume is