SIFT Physics and Simple Machines Questions and Answers 2

Question 1

An object is accelerating at 3 m/s². If the net force on it is 15 N, what is its mass?

Accepted Answer

5 kg

Answer

Using Newton's Second Law: F = ma, so m = F/a = 15/3 = 5 kg.

Question 2

What is the unit of power in the SI system?

Accepted Answer

Watt

Answer

The watt (W) is the SI unit of power, equal to one joule per second (J/s). Power measures the rate at which work is done or energy is transferred.

Question 3

An object at the top of a 50-meter cliff has potential energy of 4,900 J. What is its mass? (g = 9.8 m/s²)

Accepted Answer

10 kg

Answer

PE = mgh, so m = PE/(gh) = 4,900/(9.8 × 50) = 4,900/490 = 10 kg.

Question 4

What is the mechanical advantage of a screw with a pitch of 0.5 cm and a handle radius of 10 cm? (MA = 2πr/p)

Accepted Answer

~125.7

Answer

MA = 2πr/p = 2π(10)/0.5 = 20π/0.5 = 40π ≈ 125.7. The screw provides tremendous mechanical advantage by converting rotation into linear force.

Question 5

Two identical springs, each with spring constant k=100 N/m, are connected in parallel. What is the combined spring constant?

Accepted Answer

200 N/m

Answer

Springs in parallel have their constants added: k_total = k₁ + k₂ = 100 + 100 = 200 N/m. They share the load, making the system stiffer.

SIFT Exam Practice Test