No. Mechanical energy is not conserved. There's quite a bit of friction on the slide. So some of the potential energy is lost to heat on the way down, and the child arrives at the bottom with hot pants and less kinetic energy than you might expect.
Time = (distance) / (speed)
= (30 km) / (30 m/s)
= (30,000 m) / (30 m/s)
= (30,000 / 30) sec
= 1,000 seconds
= 16 minutes 40 seconds
Answer:
(a) 
(b) 
(c) 
Explanation:
(a) According to Newton's second law, the acceleration of a body is directly proportional to the force exerted on it and inversely proportional to it's mass.
(b) According to Newton's third law, the force that the sled exerts on the girl is equal in magnitude but opposite in the direction of the force that the girl exerts on the sled:
(c) Using the kinematics equation:
For the girl, we have 
and 
. So:
For the sled, we have . So:
When they meet, the final positions are the same. So, equaling (1) and (2) and solving for t:
Now, we solve (1) for 
Answer:
Point 2.
Explanation:
Potential energy is simply defined as the energy stored in an object due to its position. It is can be represented mathematically by:
P.E = mgh
Where:
P.E is the potential energy.
m is the mass of the object.
g is acceleration due to gravity.
h is the height to which the object is located.
From the above equation, we can thus say that potential energy depends on the height of the object since the mass of the object is always constant i.e as the height of the object increase, the potential energy also increases and as the height of the object decrease, the potential energy also decreases.
Now, considering the diagram in the question given, we can see that point 2 is the lowest height to which the rider is located. At this point i.e point 2, the rider will have the least potential energy.
