Mechanical Aptitude Forces and Motion Principles Questions and Answers

Question 1

An object is moving at a constant velocity of 15 m/s. According to Newton's First Law of Motion, which of the following must be true?

Accepted Answer

The net force acting on the object is zero.

Answer

Newton's First Law, the law of inertia, states that an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. If the velocity is constant, it means the acceleration is zero. According to Newton's Second Law (F=ma), if acceleration (a) is zero, the net force (F) must also be zero.

Question 2

A mechanic uses a long wrench to loosen a tight bolt. Why is it more effective to apply force at the end of the wrench's handle rather than closer to the bolt?

Accepted Answer

It increases the torque applied to the bolt.

Answer

Torque is the rotational equivalent of force and is calculated as Force × Distance from the pivot point (the bolt). By applying force at the end of the handle, the mechanic maximizes the distance, which in turn maximizes the torque applied to the bolt, making it easier to turn.

Question 3

If a person is in an elevator that is accelerating upwards, their apparent weight will be:

Accepted Answer

Greater than their actual weight.

Answer

When the elevator accelerates upward, the floor must push up on the person with a force greater than their weight to overcome inertia and cause the upward acceleration. This increased normal force is what a scale measures, so their apparent weight increases.

Question 4

Which of the following best describes the difference between centripetal force and centrifugal force?

Accepted Answer

Centripetal force is a real force pulling an object towards the center of rotation, while centrifugal force is an apparent outward force.

Answer

Centripetal force is a real, center-seeking force that is required to keep an object moving in a circular path. Examples include tension in a string or gravity. Centrifugal force is an apparent, or 'fictitious', force that an object seems to experience from its own rotating frame of reference, pushing it outward. It's a consequence of inertia.

Question 5

A 100 kg box is pushed across a floor with a constant force. If the force of friction opposing the motion is 50 Newtons, what is the net force required to accelerate the box at 2 m/s²?

Accepted Answer

250 N

Answer

First, calculate the force needed for acceleration using Newton's Second Law (F=ma): F_accel = 100 kg * 2 m/s² = 200 N. To achieve this acceleration, the applied force must overcome the friction and also provide the force for acceleration. Therefore, the total applied force is the sum of the force of friction and the acceleration force: 200 N + 50 N = 250 N.

Mechanical Aptitude Test Practice Test

Mechanical Aptitude Test Practice Test

Mechanical Aptitude Forces and Motion Principles Questions and Answers