NAPT - Navy Advanced Programs Principles of Motion and Forces Questions and Answers

Question 1

A 1,200 kg vehicle accelerates from 10 m/s to 30 m/s over a period of 5 seconds. What is the average net force acting on the vehicle during this acceleration?

Accepted Answer

4,800 N

Answer

First, calculate the acceleration (a) using the formula a = (vf - vi) / t, where vf is the final velocity, vi is the initial velocity, and t is time. So, a = (30 m/s - 10 m/s) / 5 s = 4 m/s². Next, use Newton's Second Law of Motion, F = ma, where F is force, m is mass, and a is acceleration. F = 1,200 kg * 4 m/s² = 4,800 N.

Question 2

Which of the following scenarios best illustrates Newton's First Law of Motion (the law of inertia)?

Accepted Answer

A book remains on a table until a person picks it up.

Answer

Newton's First Law of Motion states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. A book remaining at rest on a table is a direct example of this principle, as it will not move without an external force.

Question 3

A sailor uses a pulley system to lift a 50 kg crate of supplies 4 meters vertically from the dock to the ship's deck. How much work is done on the crate against gravity? (Assume g ≈ 10 m/s²)

Accepted Answer

2000 J

Answer

Work done against gravity is calculated as W = mgh, where m is mass, g is the acceleration due to gravity, and h is the vertical height. The force required to lift the crate is equal to its weight (mg). W = (50 kg) * (10 m/s²) * (4 m) = 2000 Joules.

Question 4

A projectile is fired from a naval gun with an initial velocity. Neglecting air resistance, which of the following statements is true about its motion?

Accepted Answer

Its horizontal velocity is constant.

Answer

In projectile motion (without air resistance), the only force acting on the object after it is fired is gravity, which acts vertically. This means there is no horizontal acceleration, so the horizontal component of the velocity remains constant throughout the flight. The vertical velocity changes due to gravity, and the net force is never zero while it's in the air.

Question 5

Two sailors on frictionless ice skates are at rest. Sailor A (80 kg) pushes Sailor B (100 kg), causing Sailor B to move away at a speed of 2 m/s. What is the recoil speed of Sailor A?

Accepted Answer

2.5 m/s

Answer

This scenario is governed by the principle of conservation of momentum. The total momentum before the push is zero. Therefore, the total momentum after the push must also be zero. The momentum of Sailor B is pB = mB * vB = 100 kg * 2 m/s = 200 kg·m/s. To conserve momentum, Sailor A must have an equal and opposite momentum: pA = -200 kg·m/s. The speed of Sailor A is vA = pA / mA = -200 kg·m/s / 80 kg = -2.5 m/s. The speed is the magnitude, which is 2.5 m/s.

NAPT - Navy Advanced Programs Test Practice Test

NAPT - Navy Advanced Programs Test Practice Test

NAPT - Navy Advanced Programs Principles of Motion and Forces Questions and Answers