Evan's Space

Wonders of Physics

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Amazing wind walker beast

It’s amazing to watch these strandbeasts walk and solely powered by wind.

Wind energy to mechanical energy 🙂


This is a toy version of the wind walker.

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Force required to pull the block up the inclined plane

There are 3 scenarios with slight variations.

Calculate the force F needed to pull the block up the inclined plane.

View the video below to understand how to solve these types of question.

You can also view the solutions below.

Click here to view another post related to this concept: work done to bring an object up

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N2007P1Q9 Pure Physics – Energy needed to pump water up a building

An apartment block receives water from a nearby reservoir. A pump is necessary to lift the water into a storage tank at the top of the building.

The gravitational field strength is 10 N / kg. How much energy does the pump supply to lift each kilogram of water into the tank?

GPE up 10 m

Solutions: 100J

Water will always find its own level. Hence with or without the pump, the water level in the pipe in the building will be of the same level as the reservoir. Hence, the pump is only needed to pump water up a height of 10m only (instead of the 50m).

Energy, E = mgh = 1 kg x 10 N/kg x 10m = 100 J

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Bullet embedded in wooden block


At a training exercise, a policeman fires a pistol. A bullet of mass 10.0 g leaves the pistol horizontally at a speed of 500 ms-1. The bullet strikes and gets embedded in a stationary piece of wood of mass 1.0 kg which was suspended. Immediately after impact, the wood with the embedded bullet moves at a horizontal speed of 5.0 ms-1 and swings upwards to a vertical height of h from its initial position before stopping momentarily.

a) What is the initial kinetic energy of the bullet when it leaves the pistol?
b)What is the final kinetic energy of the wood and embedded bullet immediately after impact?

c) By comparing (a) and (b), what is the loss in kinetic energy? Account for this loss.
d) Calculate the vertical height, h, stating any assumption made. Assume the gravitational field strength is 10 N kg-1.


a) 1250 J

b) 12.6 J

c) 1240 J. The loss in kinetic energy is converted to heat and sound energy when the bullet strikes the wood and is embedded.

d) 1.25 m