A small 20-kg canoe is floating downriver at a speed of 2 m/s. 40 J is the canoe’s kinetic energy.
Answer: Option A
<u>Explanation:</u>
The given canoe has the mass and is being given to move at a speed. Therefore the kinetic energy of the canoe can be calculated using the following method,
Given that mass of the canoe = 20 kg and its speed =1 m/s
As we know that the Kinetic energy has the formula,

Therefore, substituting the value into the equation, we get,
= 40 J
I would said A is the best option if i’m wrong sorry
Answer:
The velocity of the skateboard is 0.774 m/s.
Explanation:
Given that,
The spring constant of the spring, k = 3086 N/m
The spring is stretched 18 cm or 0.18 m
Mass of the student, m = 100 kg
Potential energy of the spring, 
To find,
The velocity of the car.
Solution,
It is a case of conservation of energy. The total energy of the system remains conserved. So,






v = 0.774 m/s
So, the velocity of the skateboard is 0.774 m/s.
The answer is c.
Sound, light and heat energy.
Hope this helped :)
I attached the missing picture.
The force of seat acting on the child is a reaction the force of child pressing down on the seat. This is the third Newton's law. The force of a child pressing down the seat and the force of the seat pushing up on the child are the same.
There two forces acting on the child. The first one is the gravitational force and the second one is centrifugal force. In this example, the force of gravity is always pulling down, but centrifugal force always acts away from the center of circular motion.
Part AFor point A we have:

In this case, the forces are aligned, centrifugal is pointing up and gravitational is pulling down.
Part BAt the point, B situation is a bit more complicated. In this case force of gravity and centrifugal force are not aligned. We have to look at y components of this forces, y-axis, in this case, is just pointing upward.
Part CThe child will stay in place at point A when centrifugal force and force of gravity are in balance: