Answer:
m = 4
Explanation:
We have,
You apply a force of 600 N to the branch which acts as a lever. It means it is input force, IF = 600 N
The rear of the truck weighs 2,400 N. It means it is output force, OF = 2400 N
The ratio of output force to the input force is equal to the mechanical advantage of the lever arm. It is given by :

So, the mechanical gain of the lever arm is 4.
When light travels from a medium with higher refractive index to a medium with lower refractive index, there is a critical angle after which all the light is reflected (so, there is no refraction).
The value of this critical angle can be derived by Snell's law, and it is equal to

where n2 is the refractive index of the second medium and n1 is the refractive index of the first medium.
In our problem, n1=1.47 and n2=1.33, so the critical angle is
b) 4m/s/s
This is because you divide the speed you reach, by the time it takes to get to that speed:
12m/s ÷ 3s = 4m/s/s
The units come from what you divide, meters per second ÷ seconds this can be written as m/s/s or ms-²