The question is poor.
It expects you to choose 'B', but things aren't nearly that simple.
We picture all of the asteroids bunched up in a neat bunch between
the orbits of Mars and Jupiter, with each asteroid following its own
nearly circular orbit. But many asteroids have wildly non-circular
'eccentric' orbits, sometimes being closer to the sun than the Earth is.
You know how you hear so much discussion about when did the Earth
get hit by an asteroid ? and when will the Earth be hit by another asteroid ?
and what will happen when the Earth is hit by an asteroid again ? None
of that would be possible if asteroids all had nearly circular orbits.
We picture comets as having these loooong skinny orbits, spending
most of every orbit waaay out in the solar system, and then dipping
close to the sun for a few days, and then going back waaaay out again.
But there are also many comets in nearly circular orbits around the sun.
You never hear anything about them, because you can never see them
without a powerful telescope, and they never do anything exciting.
So some comets could be a correct answer to this question too.
And since meteoroids are the remains of old comets, and follow the
orbit of the comet that they chipped off from, there are a lot of meteoroids
in circular orbits too, and they could also be a correct answer to this question.
Answer:
Explanation:
Consider the initial position of the frog (20 m above ground) as the reference position. All measurements are positive measured upward.
Therefore,
u = 10 m/s, initial upward velocity.
H = - 20 m, position of the ground.
g = 9.8 m/s², acceleration due to gravity.
Part (a)
When the frog reaches a maximum height of h from the reference position, its velocity is zero. Therefore
u² - 2gh = 0
h = u²/(2g) = 10²/(2*9.8) = 5.102 m
At maximum height, the frog will be 20 + 5.102 = 25.102 m above ground.
Answer: 25.1 m above ground
Part (b)
Let v = the velocity when the frog hits the ground. Then
v² = u² - 2gH
v² = 10² - 2*9.8*(-20) = 492
v = 22.18 m/s
Answer: The frog hits the ground with a velocity of 22.2 m/s
Answer:
4 m/s
Explanation:
From the law of conservation of momentum,
Total momentum before collision = Total momentum after collision
mu+m'u' = V(m+m')...................... Equation 1
Where m = mass of the arrow, u = initial velocity of the arrow, m' = mass of the apple, u' = initial velocity of the apple, V = Final velocity of the apple and the arrow after collision.
make V the subject of the equation
V = (mu+m'u')/(m+m').................... Equation 2
Given: m = 0.5 kg, m' = 2 kg, u = 20 m/s, u' = 0 m/s(initially at rest)
Substitute into equation 2
V = (0.5×20+2×0)/(2+0.5)
V = 10/2.5
V = 4 m/s.
Hence the final velocity of the apple and the arrow after the collision = 4 m/s
The force of gravity and the force of air
