7. A 10 kg block is initially at rest. A 23.5 N is applied to the right and the block is observed to be moving with constant speed. 10 kg p Q: what is the acceleration of the block? Explain your answer. Q: Is friction acting on the block? Explain. Q: Calculate the friction force acting on the block. Is it static or kinetic? Q: Draw a FBD of the block 8. A 10 kg block is initially at rest. A 23.5 N is applied to the right and the block is observed to be uniformly accelerating at 2 m/s. 10 kg de Q: Is friction acting on the block? Explain. Q: Using Newton's second law SF=ma calculate the friction force acting on the block. PART B - WORK & ENERGY 1. Define Work in physics; what is its SI unit? 1 2. Force F = 40 N is pulled at an angle q= 60 or . How much work is done by the force F, if the block is displaced 50m? 131 3. Define potential energy; what is its SI unit? What is the formula for gravitational potential energy? 4. Define kinetic energy; what is its SI unit? What is the formula for kinetic energy? 5. What is meant by mechanical energy? 6. Is the total energy of an isolated system always conserved? 7. Is the total mechanical energy of an isolated system always conserved? 8. Refer to the following: An object (m=100kg) is initially at rest at point A and starts to move long a frictionless track 200 m 160 m Set PE=0 at the ground level ie at point B a. Calculate the potential energy of object at points A, B and C b. Calculate the kinetic energy of object at points A, B, and C c. Apply conservation of energy to determine its speed when it reaches point C.