Answer: D. 25 m/s Downward
Explanation:
V = (g)(t)
V = (9.8 m/s²)(2.5)
V = 24.5 m/s
The chair does not move along the vertical direction: this means that the net force on the vertical direction is zero.
There are three forces acting along the vertical direction:
- The weight, acting downward: 
- The component of the force F perpendicular to the floor, acting downward: 
- The normal force N, acting upwards.
Since the net force must be zero, we have:
From which we can find the value of N:
Answer:
The oldest stars in spiral galaxies are younger than the oldest stars in elliptical galaxies.
Explanation:
Spiral galaxies have a greater star formation than elliptical galaxies, since the latter contain less gas and dust. Therefore, the rate of creation of new stars is lower in elliptical galaxies. These galaxies are dominated by old stars, with a long evolution. While the spiral galaxies have stars with a faster evolution.
Answer:
Explanation:
a )
one kg of coal gives energy of 27 x 10⁶ J
75 kg of coal gives energy of 27 x 10⁶ x 75 J
So rate which energy is coming out of coal per second
= 27 x 10⁶ x 75 J
= 2025 x 10⁶ J /s
2025 million watts .
b ) energy output = 800 million watts
efficiency = (800 / 2025) x 100
= 39.5 % .
