Lever: a bar used to move something
Wedge: a tool used to go in between object to put them in place
Incline plane : a ramp it’s used to help rise heavy things
Pulley: it’s a wheel that supports movement and change of direction
Answer:
A) The crossbeam is moving relative to the observer on the platform so the height appears contracted.
Explanation:
The observer on the train and the beam are in the same reference frame. That means observer on the train will measure the proper length of the beam not the contracted length . the observer is outside and the plank is in the moving system,it will appear to be moving.
The gravitational force between two objects is given by

where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is the separation between the two objects
In this problem,

,

and

, therefore the gravitational force between the two objects is
Answer:
option (B)
Explanation:
Intensity of unpolarised light, I = 25 W/m^2
When it passes from first polarisr, the intensity of light becomes

Let the intensity of light as it passes from second polariser is I''.
According to the law of Malus

Where, θ be the angle between the axis first polariser and the second polariser.

I'' = 11.66 W/m^2
I'' = 11.7 W/m^2