Write TRUE if the statement is correct and FALSE if the statement is incorrect for the following physics concepts: 1. Gravity as non-contact force. 2. Newton's second law. 3. Screw velocity ratio. 4.

Here are the solutions to your physics questions:

Direction I: Write TRUE if the statement is correct and FALSE if the statement is incorrect.

1. A force due to gravity is non-contact force.

   • Answer: True (Gravity acts without physical contact.)

2. Newton's second law formula is $F=ma$.

   • Answer: True (This is the standard formula for Newton's second law of motion.)

3. Velocity ratio of screw is $VR = \frac{2\pi R}{2\pi r}$.

   • Answer: False (The velocity ratio of a screw jack is typically $\frac{2\pi L}{p}$, where $L$ is the length of the effort arm and $p$ is the pitch of the screw. The given formula simplifies to $\frac{R}{r}$, which is not correct for a screw.)

4. The machine is speed multiplier if mechanical advantage is MA > 1.

   • Answer: False (If the mechanical advantage (MA) is greater than 1, the machine multiplies force. If MA is less than 1, it multiplies speed.)

5. Kinetic energy given by $KE=mgh$.

   • Answer: False ($mgh$ is the formula for gravitational potential energy. Kinetic energy is given by $KE = \frac{1}{2}mv^2$.)

6. Effort is the force you exert on a machine.

   • Answer: True (Effort is the input force applied to a machine.)

7. Efficiency = $\frac{\text{Mechanical advantage}}{\text{velocity ratio}}$.

   • Answer: True (Efficiency is also defined as the ratio of mechanical advantage to velocity ratio, $\eta = \frac{MA}{VR}$.)

8. Static friction is less than kinetic friction.

   • Answer: False (Static friction is generally greater than or equal to kinetic friction. It takes more force to start an object moving than to keep it moving.)

9. Power = $\frac{\text{work done}}{\text{time taken}}$.

   • Answer: True (This is the definition of power.)

10. Mechanical energy is the sum of kinetic energy and potential energy.

    • Answer: True (Mechanical energy is the total energy of motion and position.)

Direction II: Choose the best answer from the given alternatives and write in a capital letter.

11. What is the acceleration of 10kg block when acted on by force of 50N?