Answer:
If the system consists of the block only, the work done by the gravity is negative.
If the system consists of the block and the earth the work done by the gravity is zero.
Explanation:
If the system consists of the block only, then the system experiences two external forces: one exerted by the hand that lifts the block vertically upward and other exerted by the earth (gravity), which is opposed to the movement of the system, so the work done by gravity is negative.
On the other hand, if the system consists of the block and the earth, then only exists a external force which is the exerted by the hand. So, the force exerted by gravity is zero.
Wires or silver and copper
Answer:
<em>500Joules</em>
Explanation:
Kinetic energy = 1/2mv²
m is the mass of the wood
v is the velocity
Given
Mass = 10kg
Velocity v = 10m/s
Substitute into the formula and get KE
KE = 1/2 * 10 * 10²
KE = 1/2 * 1000
KE = 500Joules
<em>Hence the kinetic energy of the wood during delivery is 500Joules</em>
