A 10 gram ball is rolling at 3 m/s. The ball has energy. Calculate it. A 10 gram ball is held 2 meters from the ground. It has energy. Calculate it. You serve a volleyball with a mass of 2100 g. The ball leaves your hand with a velocity of 30 m/s. The ball has energy. Calculate it. A toy baby carriage is sitting at the top of a hill that is 21 m high. The carriage with the baby has a mass of 200 grams . The carriage has energy. Calculate it. A toy car is traveling with a velocity of 4 m/s and has a mass of 1120 g. The car has energy. Calculate it. A cinder block is sitting on a platform 20 m high. It has a mass of 790 grams. The block has energy. Calculate it. There is a bell at the top of a tower that is 5 m high. The bell has a mass of 190 grams. The bell has energy. Calculate it. A toy roller coaster is at the top of a 2 m hill and has a mass of 9660 grams. The coaster (at this moment) has energy. Calculate it.

The answer to all the questions on potential energy and kinetic energy have been done below;

A) We are told that the ball is rolling. An object in motion has kinetic energy. Formula for kinetic energy is;

K =  ½mv²

We have; m = 10 g = 0.01 kg and v = 3 m/s

K = ½ × 0.01 × 3²

K = 0.045 J

B) We are told that the ball is held at a height. This means it is at rest and any object at rest has Potential Energy. Formula for potential energy is;

PE = mgh

We have; m = 10g = 0.01 kg and h = 2 m

PE = 0.01 × 9.8 × 2

PE = 0.196 J

C) Like in A above, the ball is in motion. Thus, it has kinetic energy.

K = ½ × 2.1 × 30²

K = 945 J

D) The baby carriage is sitting at rest and therefore has potential energy.

PE = 0.2 × 9.8 × 21

PE = 41.16 J

E) The toy car is in motion and has kinetic energy. Thus;

K = ½ × 1.12 × 4²

K = 8.96 J

F) The cinder block is sitting at rest and has potential energy. Thus;

PE = 0.79 × 9.8 × 20

PE = 154.84 J

G) The bell is at the top of the tower and is at rest and thus has potential energy.

PE = 0.19 × 9.8 × 5

PE = 9.31 J

g) The rollercoaster is at the top at rest and so has potential energy.

PE = 9.66 × 9.8 × 2

PE = 189.336 J

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a) KINETIC ENERGY   K = 0.045 J , b) POTENTIAL ENERGY  U = 0.196 J ,

c)  KINETIC ENERGY  K = 9.45 10⁵ J, d) POTENTIAL ENERGY ,    U = 41.16 J ,

e) POTENTIAL ENERGY  U = 154.84 J , f)  ENERGY IS POTENTIAL    U = 9.31 J

g) energy is POTENTIAL   U = 189.336 J

Explanation:

a) The ball is moving with a speed, so it has KINETIC ENERGY

          K = ½ m v²

          K = ½ 10 10⁻³ 3²

          K = 0.045 J

b) The ball is at a given height therefore it has POTENTIAL GRAVITATORY ENERGY

           U = m g y

           U = 10 10-3 9.8 2

           U = 0.196 J

c) The ball has speed so it has KINETIC ENERGY

           K = ½ m v²

           K = ½ 2,100 30²

           K = 9.45 10⁵ J

d) The baby carriage is at a height whereby the POTENTIAL ENERGY

           U = mg h

           U = 0.200 9.8 21

           U = 41.16 J

e) the concrete block is at a height that has POTENTIAL ENERGY

           U = m g h

           U = 0.790 9.8 20

           U = 154.84 J

f) the hood has height, the ENERGY IS POTENTIAL

           U = 0.190 9.8  5

           U = 9.31 J

g) The roller coaster has height and speed, therefore the mechanical energy has a scientific part and a potential part, in general the speed at the top of the mountain is very small, so we can consider that almost all the energy is POTENTIAL

The value they give allows calculating the potential energy

            U = 9.660 9.8 2

            U = 189.336 J

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