Answer:
a= - 6.667 m/s²
Explanation:
Given that
The initial speed of the box ,u= 20 m/s
The final speed of the box ,v= 0 m/s
The distance cover by box ,s= 30 m
Lets take the acceleration of the box = a
We know that
v²= u ² + 2 a s
Now by putting the values in the above equation we get
0²=20² + 2 a x 30

a= - 6.667 m/s²
Negative sign indicates that velocity and acceleration are in opposite direction.
Therefore the acceleration of the box will be - 6.667 m/s² .
Answer:
The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.
Explanation:
Given that,
Wavelength = 400 nm
Energy 
We need to calculate the longest wavelength of light that is capable of ejecting electrons from that metal
Using formula of energy


Put the value into the formula



Hence, The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.