Answer:
Therefore it is save to carry a 62kg adult
Explanation:
From the question we are told that:
Mass 
Height of supporting Rock 
Length of Board
Mass of board 
Mass of adult
Generally the moment of balance about wedge part about is mathematically given by



where

therefore

if N=0 at fallen person

Therefore it is save to carry a 62kg adult
A) A concave mirror forming a larger, virtual image
Explanation:
The figure is missing; see attachment.
There are two types of mirror:
- Concave (converging) mirrors: a concave mirror is a mirror that reflects the light inward
- Convex (diverging) mirrors: a convex mirror is a mirror that reflects the light outward
The image formed by a mirror can also be of two types:
- Real image: it is formed on the same side of the object, with respect to the mirror
- Virtual image: it is formed on the opposite side of the object, with respect to the mirror
In the figure of this problem (see attachment), we see that:
- The mirror reflects the light from the object inward --> so it is a concave mirror
- The image is formed on the other side of the mirror --> it is a virtual image
So the correct option is
A) A concave mirror forming a larger, virtual image
Learn more about mirrors:
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Answer:
Option A
Explanation:
The Equation represents the displacement of the object which is represented by x

so,
means when time is zero so we replace t with zero in the equation,

now for v which is velocity we need to differentiate the function as the formula for velocity is rate of change of displacement over time so we derivate the equation once and get,

now for
we insert t = 0 and get

now for a which is acceleration the formula of acceleration is rate of change of velocity over time, so we differentiate the the equation of v(velocity) once or the equation of x(displacement) twice so now we get,

so Option A is your answer.
Remember derivative of a constant is always zero because a constant value has no rate of change has its a constant hence the derivative is 0
Answer:
Time taken = 10400 s
Explanation:
Given:
Initial speed of the train, 
Final speed of the train, 
Displacement of the train, 
Using Newton's equation of motion,

Now, using Newton's equation of motion for displacement,

Now, plug in the value of
in the above equation. This gives,

Now, plug in 234000 m for
, 25 m/s for
and 20 m/s for
. Solve for
.

Therefore, the time taken by the train is 10400 s.
Explanation:
Below is an attachment containing the solution.