Question

50 Points!

Answer 1

Answer:

The work done on an object arises from a force applied over a distance ... the frictional force on the tires is equal to the kinetic energy of the car, KE=1/2 ... As an example, consider an apple of mass m which is initially a height h above the ground. ... held motionless so that the initial mechanical energy is Etop = PEtop = mgh.

Explanation:

Answer 2

Answer:

1. It has more potential energy

2. Both potential energy and kinetic energy are equal.

3. It has more kinetic energy.

4. 784 J

5. 392 J

6. 392 J

7. 784 J

Explanation:

Potential energy (PE) is computed as: m*g*h

where m refers to mass, g to the gravitational acceleration (9.81 m/(s^2)) and h to height of the ball.

Kinetic energy (KE) is computed as: 1/2*m*v^2

where v refers to velocity of the ball.

1. It has more potential energy. Before the fall starts all the energy of the ball is potential energy, that is because its velocity is zero an its height is maximum.

2. As the ball falls all potential energy lost is equivalent to kinetic energy gain; when the ball is half way through its fall, both PE and KE are equal. That is, at the beginning all is potential energy, as ball falls PE starts to decrease, but KE starts to increase, so that, the addition of both equal the initial potential energy.

3. It has more kinetic energy. Just before the ball hits the ground, its height is near zero, then its PE is neglected, therefore, all the initial PE is now KE.

4. PE = m*g*h  = 2*9.81*40 = 784 J

5.  PE = m*g*h  = 2*9.81*20 = 392 J

6. KE = 1/2*m*v^2 = 1/2*2*(19.8)^2 = 392 J

7. KE = 1/2*m*v^2 = 1/2*2*(28)^2 = 784 J