Physics Practice: Machines (Mock Test 4 - Expert)
1. Expert Analysis: In a block and tackle system of 5 pulleys, the lower block has a mass of $1.5 \text{ kg}$. If a load of $15 \text{ kg}$ is lifted, the efficiency of the system (ignoring friction in bearings) is:
2. Experimental Setup: A student uses a single movable pulley to lift a load. He notices the effort is applied upwards. To apply the effort downwards, he adds a fixed pulley. How does this addition affect the Mechanical Advantage (M.A.) and Velocity Ratio (V.R.) ideally?
3. Clinical Logic: While using a physical balance, the "knife edge" is made sharp and the beam is made light. This is done to:
4. Data-Based: A machine with $V.R. = 4$ lifts a load of $100 \text{ kgf}$ through a distance of $2 \text{ m}$ in $5 \text{ seconds}$ with an efficiency of $80\%$. The Power input to the machine is: (Take $g = 10 \text{ m/s}^2$)
5. In a block and tackle system, if the number of pulleys is even, the string is tied to the:
6. A jack-screw used to lift a car is a combination of which simple machines?
7. Expert Calculation: A lever of length $200 \text{ cm}$ has a fulcrum at $40 \text{ cm}$ from one end. If it is used as a Class II lever, the Mechanical Advantage is:
8. Which of the following is true for a Class III lever?
9. Experimental Observation: In a block and tackle system, as the number of pulleys increases, the efficiency typically:
10. For a given machine, if the work input is doubled and the work output is tripled, the efficiency:
11. A single movable pulley has a mass of $m$. The effort required to lift a load $L$ is:
12. Which lever class has the same direction for both Load and Effort?
13. The M.A. of a Class I lever is $0.5$. This lever acts as a:
14. To lift a load of $60 \text{ kgf}$ using a block and tackle with $V.R. = 3$ and efficiency $80\%$, the effort needed is:
15. A simple machine helps in gaining speed if:
16. The $V.R.$ of a system of 5 pulleys is 5. If the load is moved up by $10 \text{ cm}$, the effort end moves by:
17. In a pair of fire tongs, the distance of the fulcrum from the load is $15 \text{ cm}$ and from the effort is $5 \text{ cm}$. The M.A. is:
18. Total mechanical energy is conserved in a machine if:
19. A worker uses a pulley system of $V.R. = 2$ to lift a $100 \text{ N}$ load. If he pulls the rope with $60 \text{ N}$, the work done against friction to lift the load by $1 \text{ m}$ is:
20. The Velocity Ratio of a machine is $10$. It means the effort arm is ________ than the load arm for a Class I lever.