Explanation:
average speed = total distance travelled / total time travelled
time to travel the first 6km: 6 / 50 = 3/25 (h)
time to travel the next 6km: 6 / 90 = 1/15 (h)
[I think there's problem in the question 'cause 900km/h sounds impossible for normal person to travel in normal condition]
The total time: 3/25 + 1/15 = 14/75 (h)
Average speed over the 12 km drive will be:

Mechanical energy E = mgh + 1/2mv²
When he starts, let h = 0 ⇒ E₁ = 1/2mv₁²
When he reaches height h ⇒ E₂ = mgh + 1/2mv₂²
Without friction, energy is conserved at all times.
E₁ = E₂
↓
1/2mv₁² = mgh + 1/2mv₂²
↓
1/2v₁² = gh + 1/2v₂²
↓
gh = 1/2(v₁² - v₂²)
↓
h = (v₁² - v₂²) / (2g)
Answer:
The value is
Explanation:
From the question we are told that
The mass is
The needed oscillation time is
Generally the spring constant is mathematically represented as

=> 
=>
I’ve had a question like this and i put c
Answer:
angle of incidence for the second mirror is 55.4 degree
Explanation:
Given data;
Angle between two mirror is 90 degree
Incident angle on first mirror is 34.6 degree
For first mirror
Angle of incidence is equal to angle of reflection
34.6 degree = angle of reflection

Now , for the triangle ABC [from figure]



The angle of incidence for
angle of incidence for the second mirror is 55.4 degree