A 45.00 kg child standing on a frozen pond throws a 0.60 kg stone to the east with a speed of 5.80 m/s. Neglecting friction between child and ice, what is the speed (in m/s) of the child after throwing the stone?
I'm kind of confused about the masses..
What confuses you about the masses?
They they you what they are.
Total momentum is conserved and remains zero.
That means the stone and the child, after the stone is thrown, have equal and opposite momenta.
45*Vchild = -0.6*Vstone = -3.48 kg m/s
Vchild = -3.48/45 = -____ m/s
The minus sign means the child goes backwards, relative to the thrown stone direction. Since that only ask for the speed, you can forget about the minus sgn.
i read the question wrong..thank for the help
To find the speed of the child after throwing the stone, we can use the principle of conservation of momentum. According to this principle, the total momentum before and after the stone is thrown should be the same since there is no external force acting on the system (child + stone).
Momentum is calculated by multiplying the mass of an object by its velocity. The momentum of the child before throwing the stone is given by:
Initial momentum of child = mass of child × initial velocity of child
The momentum of the stone is given by:
Initial momentum of stone = mass of stone × initial velocity of stone
The momentum of the system (child + stone) after the stone is thrown is given by:
Final momentum of system = total mass of system × final velocity of system
Since momentum is conserved, the initial total momentum should be equal to the final total momentum:
Initial momentum of child + Initial momentum of stone = Final momentum of system
Now let's substitute the given values into the equation.
The mass of the child is given as 45.00 kg, and the mass of the stone is given as 0.60 kg. The initial velocity of the child is not mentioned, but we can assume it is at rest (0 m/s) since no information is provided. The initial velocity of the stone is given as 5.80 m/s. The final velocity of the system is the speed of the child after throwing the stone, which we need to find.
Plugging in these values into the conservation of momentum equation, we have:
(45.00 kg × 0 m/s) + (0.60 kg × 5.80 m/s) = (45.00 kg + 0.60 kg) × final velocity of system
Simplifying the equation:
0 + 3.48 kg m/s = 45.60 kg × final velocity of system
Now we can solve for the final velocity of the system:
(3.48 kg m/s) / 45.60 kg = final velocity of system
Final velocity of system = 0.0762 m/s (rounded to four decimal places)
Therefore, the speed of the child after throwing the stone is approximately 0.0762 m/s.