Question

A roller weighing 80 kg moves with a speed of 20 m/s. What is the kinetic energy possessed by the stone?

Answer 1

Answer:

KE= 16000Nm

Explanation:

KE=1/2*m*v^2

=1/2*80*(20)^2

=40*400

=16000 Nm or 16000 J

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Answer 2

Correct QuEstion: A roller weighing 80 kg moves with a speed of 20 m/s. What is the kinetic energy possessed by the roller?

Given that:

• Mass = 80 kilograms
• Velocity = 20 m/s

To calculate:

• Kinetic energy

Solution:

• Kinetic energy = 16000 J

Using concept:

• Formula of kinetic energy

Using formula:

• ${\sf{E_k \: = \dfrac{1}{2}mv^{2}}}$

Where, E_k denotes kinetic energy, m denotes mass, v denotes velocity

Full solution:

$:\implies \sf E_k \: = \dfrac{1}{2}mv^{2} \\ \\ :\implies \sf E_k \: = \dfrac{1}{2} \times 80 \times 20 \times 20 \\ \\ :\implies \sf E_k \: = \dfrac{1}{2} \times 80 \times 400 \\ \\ :\implies \sf E_k \: = \dfrac{1}{2} \times 32000 \\ \\ :\implies \sf E_k \: = 16000 \: J \\ \\ :\implies \sf Kinetic \: energy \: = 16000 \: Joules$

Additional information:

• Work - If a body get displaced when a force acts on it, work it said to be done. Work is measured by the product of force and displacement of the body along the direction of force. If a body get displaced by S when a force F act's on it, then the work W = ${\sf{FS \: cos \theta}}$

Where, Ø denotes angle between force and displacement

If both force and displacement are in the same direction, then W = FS.

• Work is a scaler quantity and it's SI unit is joules.

• Energy = Capacity of doing work by a body is called it's energy. Energy is a scaler quantity & it's SI unit is ${\sf{joule}}$ Energy developed in a body due to work done on it is called mechanical energy. Mechanical energy is of two types –

• Potential energy
• Kinetic energy

➜ Potential energy = The capacity of doing work developed in a body due to it's position or configuration is known as potential energy like, ⑴ energy of stretched or compressed string ⑵ energy of spring in a watch ⑶ energy of water collected at a height.

PE of a body is the gravitational field of earth is ${\sf{mgh}}$

[Where, m denotes mass , g denotes acceleration due to gravity and h denotes height of the body from the surface of the earth].

➜ Kinetic energy = Energy posses by a body due to it's motion is called kinetic energy of the body. If a body of mass is moving with speed then kinetic energy of body is ${\sf{\dfrac{1}{2}mv^{2}}}$

Where, m denotes mass and v denotes speed

Relationship between momentum and the kinetic energy:

${\sf{K.E \: = \: \dfrac{p^{2}}{2m}}}$