Answer:
1) 1.31 m/s2
2) 20.92 N
3) 8.53 m/s2
4) 1.76 m/s2
5) -8.53 m/s2
Explanation:
1) As the box does not slide, the acceleration of the box (relative to ground) is the same as acceleration of the truck, which goes from 0 to 17m/s in 13 s
2)According to Newton 2nd law, the static frictional force that acting on the box (so it goes along with the truck), is the product of its mass and acceleration
3) Let g = 9.81 m/s2. The maximum static friction that can hold the box is the product of its static coefficient and the normal force.
So the maximum acceleration on the block is
4)As the box slides, it is now subjected to kinetic friction, which is
So if the acceleration of the truck it at the point where the box starts to slide, the force that acting on it must be at 136.6 N too. So the horizontal net force would be 136.6 - 108.3 = 28.25N. And the acceleration is
28.25 / 16 = 1.76 m/s2
5) Same as number 3), the maximum deceleration the truck can have without the box sliding is -8.53 m/s2
Answer:
Explanation:
A positive v time graph is a velocity graph. If the position/time is negative, then the slope of the line is negative. If the line is indicative of the velocity, which it is, that means that the velocity is negative (decreasing). The first choice is the one you want.
Answer:
If the cosmos emerged from the Big Bang with sufficiently high density, then it contains enough matter to halt its own expansion and the recession of galaxies will stop. Red shifts will turn to blue shifts as the universe begins collapsing inward and stars and planets and galaxies will collide with increasing frequency and violence as space diminishes. The entire universe will shrink towards a super dense, super hot singularity, much like the one from which it originated, the "big crunch".
Gravity of a low density universe will be too weak to half the present expansion. The universe will expand forever, the galaxies continually receding, their radiation steadily weakening with increasing distance.
In time, we will see no galaxies in the sky beyond the Local Group. Eventually, the Local Group will peter out as their fuel supply is consumed. A "cold death" will happen whereby all radiation, matter, and life are eventually destined to freeze. This would take about a trillion years to happen.
The universe can expand forever, in which case we die a cold death in which all activity gradually fades away, or the expansion can stop and the universe will recollapse to a fiery Big Crunch.
