Answer:
the kinetic energy of body B is twice the kinetic energy of body A
Explanation:
The kinetic energy of a body is given by
K = ½ m v²
If two objects leave the same point, suppose that at the same height when they reach the ground they have the same velocity.
Therefore if the mass of body b is twice the mass of body A
= ½ (2 
) v²
K_{b} = 2 (½ m_{a} v²)
K_{b} = 2 K_{a}
therefore the kinetic energy of body B is twice the kinetic energy of body A
Answer:
60 N
Explanation:
because when we double the 30N, we will get 60N as a force
Answer:
D. The motion cannot be determined without knowing the speeds of the objects before the collision.
Explanation:
This question is tricky! We know the object moving to the left has a greater mass than the one moving to the right. We'd <em>assume</em> they would move to the left because the leftwards object has a greater mass, right?
Not. So. Fast.
We can solve for the objects' final velocity using the formula for momentum, m₁v₁ + m₂v₂ = (m₁ + m₂)v .
Now here's where the trap is sprung: <em>we don't think about the equation</em>. This shows that the final velocity of the objects and the direction depends on both the mass of the objects <em>and</em> their initial velocity.
Basically, what if the 3 kg object is moving at 1 m/s and the 4 kg object is moving at –0.5 m/s? The objects would move to the <em>right</em> after the collision!
Do we know the velocity of these objects? No, right?
That means we <em>can't</em> determine the direction of their motion <u>unless we know their initial, pre-collision velocity</u>. This question is tricky because we look at the 4 kg vs. 3 kg and automatically assume the 4 kg object would dictate the direction of motion. That's not true. It depends on velocity as well.
I hope this helps you! Have a great day!
