Answer:
6.46393559312 m/s²
Explanation:
Time taken to cover 56 m

Distance covered in 0.42 seconds

From equation of linear motion


The minimum acceleration is 6.46393559312 m/s²
Let's assume that ground level is the height 0 meters. The change in potential energy is going to be gravitational potential energy, which is given by PE=mgh.
ΔPE=mgh-mgy
=mg(h-y)
=50(28-0)
=1400 J
Answer:
25 m/s
Explanation:
This question can be solved using equation of motion

where
v is the final velocity
u is the initial velocity
s is the distance covered while moving from initial to final velocity
a is the acceleration
_____________________________________________
Given
box moved for distance of 62.5 m
Friction slows the box at –5.0 m/s2----> this statement means that there is deceleration , speed of truck decreases by 5 m/s in every second until the box comes to rest. Friction causes this deceleration.
thus in this problem
a = -5.0 m/s2
V = 0 as body came to rest due to friction deceleration
u the initial velocity we have to find
the initial velocity of box will be the same as speed of truck, as the box was in the truck and hence box will pick the speed of truck.
so if we find speed of box, we will be able get sped of truck as well.
using equation of motion

Thus, initial speed with the truck was travelling was 25 m/s.
The answer is in the attachment
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