A thread holds a 1.5-kg and a 4.50-kg cart together. After the thread is burned, a compressed spring pushes the carts apart, giving the 1.5 kg cart a speed of 26 cm/s to the left. What is the velocity of the 4.5-kg cart? a. 10 cm/s b. 4.56 cm/s c. 8.67 cm/s d. 7.3 cm/s

Respuesta :

Answer:

c. 8.67 cm/s

Explanation:

From the law of conservation of momentum,

Total momentum before the thread was burned = Total momentum after was burned

mu + m'u' = mv + m'v'...................... Equation

Where m = mass of the heavier cart, m' = mass of the lighter cart, u = initial velocity of the bigger cart, u' = initial velocity of the smaller cart, v = final velocity of the bigger cart, v' = final velocity of the smaller cart.

Note: Both cart where momentarily at rest, as  such u = u' = 0. i.e the total momentum before the thread was burn = 0

And assuming the left is positive,

We can rewrite equation 1 as

mv + m'v' = 0............................................ Equation 2

Given: m = 4.5 kg, m' = 1.5 kg, v' = 26 cm/s

Substitute into equation 2,

4.5v + 1.5(26) = 0

4.5v + 39 = 0

4.5v = -39

v = -39/4.5

v = -8.67 cm/s.

Note: v is negative because it moves to right.

Hence the velocity of the 4.5 kg cart = 8.67 cm/s.

The right option is c. 8.67 cm/s

The velocity of the cart which has 4.5 kg of mass is 8.67 cm/s. Option C is correct.

From the law of conservation of momentum,

[tex]mu + m'u' = mv + m'v'[/tex]

Where

[tex]m[/tex] = mass of the heavier cart = 4.5 kg

[tex]m'[/tex] = mass of the lighter cart = 1.5 kg,

[tex]u[/tex]= initial velocity of the bigger cart,

[tex]u'[/tex] = initial velocity of the smaller cart,

[tex]v[/tex] = final velocity of the bigger cart,

[tex]v'[/tex] = final velocity of the smaller cart = 26 cm/s

Since the carts were momentarily at the rest, the total momentum before the thread was burned is zero.

So,

[tex]mv + m'v' = 0[/tex]

Put the values in the formula,

[tex]4.5v + 1.5(26) = 0\\\\v =\dfrac { -39}{4.5}\\\\\v = -8.67 \rm \ cm/s.[/tex]

Therefore,  the velocity of the cart which has 4.5 kg of mass is 8.67 cm/s.

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