What is a push or pull that one object excerpts on another object?
2 answers:
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Answer:
The box stops in 0.139 seconds, after moving 7.29cm (0.0729m) backwards relative to the belt.
Explanation:
As the box is initially at rest relative to the earth, it is moving backwards with a speed of 1.05m/s relative to the belt. Then, the frictional force acts on the box to make it stop relative to the belt. So, we first have to write the equations of motion of the box in each axis:
Since the frictional force is equal to
, then we have that the acceleration is:
Now, from the definition of acceleration we get:
And, as the final velocity is zero because the box gets to a stop, we have:
(Don't worry about the negative sign. It will disappear because the initial velocity is also negative, since we take the box initially moving backwards)
Then, plugging in the given values, we calculate the time:
In words, the time the box takes to stop sliding relative to the belt is 0.139s.
The displacement of the box in this time, is given by the kinematics formula:
Finally, we calculate the displacement:
This means that the box moves 7.29cm backwards relative to the belt.
Answer:
V = 13m/s
North-East (i.e. 45 degree from North)
Explanation:
This question deals with the idea of momentum.
Since the directions of a compass are fixed, we can take south as horizontal and west as vertical. Since both pieces of coconut are of equal mass, then the resultant of the two pieces would be in between South and West and the third piece would be opposite this direction and be in the North-East (i.e. 45 degree from North) direction
To find the speed of the third piece, we first find the speed on the two pieces of the coconut in terms of (horizontal component of velocity) and
(vertical component of velocity)
We have
= Velocity in South direction = 18m/s
= Mass of piece in South direction = m
= Velocity in West direction = 18m/s
= Mass of piece in West direction = m
= Velocity of Third Piece in North direction = unknown
= Velocity of Third Piece in East direction = unknown
= Mass of third piece = 2m
Since we now know the horizontal and vertical component of the velocity of the third piece of coconut we find the resultant velocity. Since we know the direction is North-East, we can imagine a right angled triangle with base of 9 and height 9 and the hypotenuse equal to the resultant velocity .
We can simply apply the Pythagoras theorem and find the hypotenuse
V = 13m/s