Q: The efficiency of a machine is given by which formula?

$$Efficiency = \left(\frac{AMA}{IMA}\right) \times 100\%$$

Q: A screw has a handle radius of 4 cm and a pitch of 0.5 cm. What is its ideal mechanical advantage (IMA)? (Use $$IMA = \frac{2\pi r}{pitch})$$

$$IMA = \frac{2\pi \times 4}{0.5} = 50.3$$

Q: A 10 kg object is lifted to a height of 2 m. What is its potential energy? (Use $$g = 9.8\ m/s^2$)

$$PE = mgh = 10 \times 9.8 \times 2 = 196\ J$$

Question 1

Which of the following best describes a first class lever?

Accepted Answer

The fulcrum is between the effort and the load.

Question 2

A ramp is 3.0 m long and raises a load to a height of 0.75 m. What is the ideal mechanical advantage (IMA) of the ramp?

Accepted Answer

$$IMA = \frac{3.0}{0.75} = 4.0$$

Question 3

Which of the following statements about static equilibrium in simple machines is TRUE?

Accepted Answer

The sum of torques about any point is zero.

Question 4

A block-and-tackle pulley system supports a 400 N load with 4 ideal supporting rope segments. Neglecting friction, what is the ideal effort required?

Accepted Answer

$$\frac{400}{4} = 100\ N$$

Question 5

Which of the following is NOT a simple machine?

Accepted Answer

A rolling wheel on a toy car

Question 6

The efficiency of a machine is given by which formula?

Accepted Answer

$$Efficiency = \left(\frac{AMA}{IMA}ight) 	imes 100\%$$

Question 7

A lever has an effort arm of 0.8 m and a load arm of 0.2 m. What is the ideal mechanical advantage (IMA)?

Accepted Answer

$$IMA = \frac{0.8}{0.2} = 4.0$$

Question 8

Which of the following best describes a wedge?

Accepted Answer

Two inclined planes joined back-to-back, used to split or lift materials.

Question 9

A screw has a handle radius of 4 cm and a pitch of 0.5 cm. What is its ideal mechanical advantage (IMA)? (Use $$IMA = \frac{2\pi r}{pitch})$$

Accepted Answer

$$IMA = \frac{2\pi 	imes 4}{0.5} = 50.3$$

Question 10

Which of the following is a property of a third class lever?

Accepted Answer

The effort is between the fulcrum and the load.

Question 11

A 10 kg object is lifted to a height of 2 m. What is its potential energy? (Use $$g = 9.8\ m/s^2$)

Accepted Answer

$$PE = mgh = 10 	imes 9.8 	imes 2 = 196\ J$$

Question 12

Which of the following statements about energy in machines is CORRECT?

Accepted Answer

Energy transforms between types, but total energy is conserved.

Question 13

The coefficient of friction ($$\mu) is $$defined as:

Accepted Answer

$$\mu = \frac{F_{friction}}{F_{normal}}$$

Question 14

Which of the following is a valid way to increase the actual mechanical advantage (AMA) of a machine in practice?

Accepted Answer

Reduce friction with lubrication.

Question 15

A wheel and axle system has a wheel radius of 0.5 m and an axle radius of 0.1 m. What is the ideal mechanical advantage (IMA)?

Accepted Answer

$$IMA = \frac{0.5}{0.1} = 5$$

Question 16

Which of the following best describes a compound machine?

Accepted Answer

A machine made of two or more simple machines.

Question 17

A 20 kg crate rests on a rough incline at $$30^\circ. If it is $$just about to slide, what is the coefficient of static friction? (Use $$\mu = 	an 	heta)$$

Accepted Answer

$$\mu = 	an 30^\circ = 0.577$$

Question 18

Which of the following is a property of a self-locking machine?

Accepted Answer

Friction prevents back-driving when input is removed.

Question 19

Which of the following is a correct statement about Newton's Third Law of Motion?

Accepted Answer

For every action, there is an equal and opposite reaction.

Physics of Simple and Compound Machines: Study Guide

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