There is a correct answer to this question, and then there is the one they want you to choose. Which one should I give you first ?
Let's start with the correct answer:
The force of gravity on any object is
(mass of the object) times (acceleration of gravity on the planet where the object is) .
The acceleration of gravity on Earth is about 9.8 m/s², so the force of gravity on this object is
(4000 kg/m³) x (0.9 m³) x (9.8 m/s²)
= (3,600 kg) x (9.8 m/s²)
= 35,280 kg-m/s² = 35,280 Newtons.
That's the force of gravity attracting this block and the Earth toward each other. It makes no difference whether the block is in your bedroom closet, in the back yard under a pile of mulch, inside a steel safe resting on a bed of styrofoam peanuts and slivered almonds, or underwater in the neighbor's pool. That's the force of gravity on this block, and it's the correct answer to the question.
It's not one of the choices, though. That's because the question is poorly written. The person who wrote the question is unclear on the concepts, and the more you work with the question, the more unclear and confused YOU'LL become.
When the block is in water, the force of gravity on it doesn't change. BUT ... there's ANOTHER force on it ... the buoyant force ... acting upward on it, and canceling part of the force of gravity.
The buoyant force is the weight of the displaced water. The displaced water is the water that has to get out of the way when you drop the block in, so the volume of displaced water is the volume of the block.
-- The volume of the block is (0.9 m³).
-- The density of water is 1000 kg/m³, so the mass of 0.9 m³ of water is 900 kg.
-- The weight of 900 kg of water is (mass) x (gravity)
= (900 kg) x (9.8 m/s²)
= 8,820 Newtons.
When the block is in water, it feels like it's that much LIGHTER, because that's the force of the water pushing UP on the block. It's the same reason why your big brother seems so light in the pool that you can pick him up and carry him.
So how heavy does this block FEEL in water ?
The force of gravity pulling down on it: 35,280 newtons The force of water pushing up on it: 8,820 newtons How heavy the block feels (the difference) 26,460 newtons
The question is written so poorly that even THIS number is not one of the choices.
Again, the thing to realize is that being in the water does NOT change the force of gravity on anything. It only creates another force, that acts against gravity.
Just like . . . When you walk up some stairs, how does it happen that you suddenly move upward, opposite to gravity. Does the force of gravity acting on you change ? No ! But you use your leg muscles to create another force in the opposite direction, that works against gravity, and makes you seem so light that you can actually move up, opposite to gravity.
The dedicated graphics card is used when performing hardware-intensive tasks so as to ensure efficiency and balanced performance. However, it uses more power and thus produces more heat. When the cooling system is not sufficient or the room is not well ventilated, your PC begins to overheat while playing games. Explanation: How does the second law of thermodynamics relate to the direction of heat flow? Heat of itself never flows from a cold object to a hot object. ... The second law expresses the maximum efficiency of a heat engine in terms of hot and cold temperatures. one of these answers i am not sure
The answer is Carbon. Beyond being the only element listed here that is located in the second row, it is also in the fourteenth column of the table if you count from left to right. Hope this helps!
<span><span>Velocity is a vector, and the initial and final ones are in opposite directions. There must have been acceleration in order to change the direction of motion.</span>
A) No. The initial and final velocities are the same. This is all wrong, and not the correct choice. It's "Yes", and the initial and final velocities are NOT the same.
B) Yes. The ball had to slow down in order to change direction.
This is poor, and not the correct choice. The "Yes" is correct, but the explanation is bad. Acceleration does NOT require any change in speed.
C) No. Acceleration is the change in velocity. The ball's velocity is constant.
This is all wrong, and not the correct choice. It's "Yes", there IS acceleration, and the ball's velocity is NOT constant.
D) Yes. Even though the initial and final velocities are the same, there is a change in direction for the ball.
This choice is misleading too. The "Yes" is correct ... there IS acceleration. The change in direction is the reason. The initial and final velocities are NOT the same. Only the speeds are. </span>
