Answer:
When the velocity doesn't change its direction
Explanation:
Since velocity vector has 2 components: direction and magnitude, and speed is the velocity's magnitude. So if the velocity doesn't change its direction, we essentially use its magnitude, aka speed, to calculate the rate of change for acceleration.
Displacement will be 15 too because
It falls from 0 till 15 meters
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There are missing data in the text of the problem (found them on internet):
- speed of the car at the top of the hill:

- radius of the hill:

Solution:
(a) The car is moving by circular motion. There are two forces acting on the car: the weight of the car

(downwards) and the normal force N exerted by the road (upwards). The resultant of these two forces is equal to the centripetal force,

, so we can write:

(1)
By rearranging the equation and substituting the numbers, we find N:

(b) The problem is exactly identical to step (a), but this time we have to use the mass of the driver instead of the mass of the car. Therefore, we find:

(c) To find the car speed at which the normal force is zero, we can just require N=0 in eq.(1). and the equation becomes:

from which we find
Answer:
The minimum frequency required to ionize the photon is 111.31 ×
Hertz
Given:
Energy = 378 
To find:
Minimum frequency of light required to ionize magnesium = ?
Formula used:
The energy of photon of light is given by,
E = h v
Where E = Energy of magnesium
h = planks constant
v = minimum frequency of photon
Solution:
The energy of photon of light is given by,
E = h v
Where E = Energy of magnesium
h = planks constant
v = minimum frequency of photon
738 ×
= 6.63 ×
× v
v = 111.31 ×
Hertz
The minimum frequency required to ionize the photon is 111.31 ×
Hertz