At time
seconds, the mass has angular speed

and hence linear speed

After 8 s, its linear speed is

and has centripetal acceleration with magnitude

To maintain this linear speed, by Newton's second law the required centripetal force should have magnitude

<span>When a person lifts the block, the block has more potential energy. Therefore the person does positive work on the block.
work = m g h
work = (4.5 kg) (9.80 m/s^2) (1.2 m)
work = 52.92 joules
The person's work on the block is 52.92 joules
When the block is being raised, the force of gravity opposes the motion. Therefore the force of gravity does negative work on the block.
work = - (force) (h)
work = - m g h
work = -(4.5 kg) (9.80 m/s^2) (1.2 m)
work = -52.92 joules
The work done by the force of gravity on the block is -52.92 joules
Note that when the block is moved horizontally, the potential energy does not change. Therefore there is no work done on the block when it moves horizontally (we are assuming that the kinetic energy does not change).</span>
Answer:
Explanation:
Given
radius 
Charge on surface 
Point Charge inside sphere 
Electric Field at 
Treating Surface charge as Point charge and applying Gauss law

where A=surface area up to distance r


