Explantion would be appreciated. Consider an object with a mass of 400 g sliding

Question

Explantion would be appreciated.

Consider an object with a mass of 400 g sliding without friction along a hill top as shown. At a point 7 meters above the (horizontal) sea level it has a speed of 4 m/s. what is its speed when it gets to the region that is only 1 m above sealevel? 10.8 m/s 134 m/s 8.7 m/s 132 m/s 11.6 m/s When the object of the previous problem was 7 m above sea level what was its total energy (kinetic plus potential)? Assume sea levelcrresponds to the zero of gravitational potential energy 27.5 J 30.7J 76.7 J 68.4 J 92 J A spring loaded projectile launcher is pointing straight up. A 5 g projectile is loaded into the launcher. The spring with constant 40 N/m is compressed 10 cm. The system is at rest until fired. How high above the equilibrium position of the spring does the projectile travel? 40.0 m 200 m 8m 64 m 4.1 m

Explanation / Answer

total energy is always conserved ie initial total energy = final total energy taking sea level as reference for gravitational potential energy we have initial energy = mgh+1/2 mv^2 = 0.4 * 9.8 * 7 + .5 * 0.4 * 4^2=30.64 let velocity at 1 m height be v m/s so final energy = 0.4*9.8*1 + 0.5 *0.4*v^2= 3.92+0.2v^2 equating the total energies we have 30.64=3.92+0.2v^2 so v^2=133.6 so v at a height of 1m = 11.56m/s

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