The cart is given an initial push up the ramp. After this push, as the car moves up the ramp, the direction of the acceleration of the cart is the ramp. After the reaches its highest point, turns around, and begins moving down the ramp, the direction of the acceleration of the cart is the ramp. At the highest point the cart reaches on the ramp, when the cart momentarily comes to rest, the magnitude of the acceleration of the cart is .

Explanation:

The only force acting on the cart is a component of its weight parallel to ramp downwards . No other force acts parallel to the ramp .

Even when the cart is moving up after the initial push , its weight is acting downwards so acceleration is acting downwards .

When the cart is stationary at the top position , its weight is acting downwards so acceleration is downwards at that moment also . When the cart is going downwards , still its weight is acting down so acceleration is acting downwards .

After this push, as the car moves up the ramp, the direction of the acceleration of the cart is _down the ramp. After the reaches its highest point, turns around, and begins moving down the ramp, the direction of the acceleration of the cart is _down the ramp. At the highest point the cart reaches on the ramp, when the cart momentarily comes to rest, the magnitude of the acceleration of the cart is _downwards .

im sorry i dont know

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.