Answer: 4 s
Explanation:
Given
The applied force is 70 N
mass of the rock is 28 kg
initial velocity 
final velocity 
Deceleration provided by force is

using the equation of motion

m/s^2 is 39.2266
is the answer If thats what you needed
Answer:
a) 17.086m
b) 0.1671 m
Explanation:
Given data: speed of water through the hose = 1.81 m/s
through the nozzle = 18.3 m/s
We know that maximum height of an object with upward velocity v is given by,
a) H = v^2/2g
where H is the maximum height water emerges
= 18.3^2/(2×9.8) = 17.086 m answer
b) Again,
H = v^2/2g
= 1.81^2/(2×9.8) = 0.1671 m
Light will travel more slowly in a material with a higher index of refraction