A 4 kg object is moving with a speed of 5 m/s. If it comes to rest, what is the

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Question: A 4 kg object is moving with a speed of 5 m/s. If it comes to rest, what is the work done by friction?

Options:

Correct Answer: 100 J

Solution:

Work done = change in kinetic energy = 0 - 0.5 × 4 kg × (5 m/s)² = -50 J.

A 4 kg object is moving with a speed of 5 m/s. If it comes to rest, what is the work done by friction?

A 4 kg object is moving with a speed of 5 m/s. If it comes to rest, what is the work done by friction?

Step 1: Identify the mass of the object, which is 4 kg.
Step 2: Identify the initial speed of the object, which is 5 m/s.
Step 3: Calculate the initial kinetic energy using the formula: Kinetic Energy = 0.5 × mass × (speed)².
Step 4: Substitute the values into the formula: Kinetic Energy = 0.5 × 4 kg × (5 m/s)².
Step 5: Calculate (5 m/s)², which is 25 m²/s².
Step 6: Multiply 0.5 × 4 kg × 25 m²/s² to get 50 J.
Step 7: The object comes to rest, so the final kinetic energy is 0 J.
Step 8: Calculate the change in kinetic energy: Final KE - Initial KE = 0 J - 50 J.
Step 9: The change in kinetic energy is -50 J, which represents the work done by friction.

Work-Energy Principle – The work done by forces on an object is equal to the change in its kinetic energy.
Kinetic Energy Calculation – Kinetic energy is calculated using the formula KE = 0.5 × mass × velocity².
Negative Work – Work done against motion (like friction) is considered negative, indicating energy is removed from the system.