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Answer:
<em>Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.</em>
Explanation:
<u>Potential and Kinetic Energy</u>
The gravitational potential energy is the energy an object has due to its height above the ground. The formula is
Where:
m = mass of the object
g = acceleration of gravity (9.8~m/s^2)
h = height
Note we can also use the object's weight W=mg into the formula:
The kinetic energy is the energy an object has due to its speed:
Where v is the object's speed.
Initially, the object has no kinetic energy because it's assumed at rest.
The W=30 N rock falls from a height of h=40 m, thus:
Since the sum of the kinetic and potential energies is constant:
U' + K' = 1,200 J
Here, U' and K' are the energies at any point of the motion. Since both must be the same:
U' = K' = 600 J
U'=Wh'=600
Solving for h':
Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.
Answer:
The speed of second toy cart is 4 m/s.
(c) is correct option
Explanation:
Given that,
Mass of first toy cart = 2 kg
Mass of second toy cart = 6 kg
Speed of first toy cart = 12 m/s
We need to calculate the speed of second toy cart
Using formula of momentum
Where, m₁ = mass of first toy cart
m₂ = mass of second toy cart
v₁ = velocity of first toy cart
v₂ = velocity of second toy cart
Put the value into th formula
Hence, The speed of second toy cart is 4 m/s.
(c) is correct option