Unit 3 Practice Test Flashcards
Which of the following statements about Newton’s law of inertia is not correct?
An object at rest will accelerate if balanced forces are applied to it.
Which of the following events best demonstrates a balanced force?
At summer camp, two tug-of-war teams pull a rope but are so evenly matched that neither side moves.
The equation a = F/m can be rewritten as F = ma, or force equals mass times acceleration. This is Newton’s second law. Which of the following best states how this equation explains why an object accelerates?
When a net force is applied to an object, the object will accelerate; objects accelerate when they are pushed or pulled.
The Newton, N, is used to express force. It is derived from the equation F = ma, where m equals 1 kilogram and |a| equals 1 meter per second squared. A Newton, N, takes the place of F and is therefore expressed by the equation 1N = 1 kg m/s^2. Given this information, which expression for force is correct for a cart with 4 Newtons of force applied to it?
F = 4 kg m / s^2
A mass of 5.2 kg is accelerated to 4.0 m / s2 when a force of magnitude F is applied to it. If the same force is applied to another object causes it have an acceleration of 1.8 m / s2, what is the mass of this object?
12 kg
An object of mass 5 kg is experiencing an acceleration of (3i + 4j)m/s^2. How much force is applied to it?
(15i + 20j)N
What acceleration does an object with a mass of 5 kg experience under the force (10i + 20j)N?
(2i + 4j)m/s^2
An object with a mass of 5 kg is subject to two forces, (10i + 20j)N and (-5i + 10j)N. What acceleration does the object experience?
(1i + 6j)m/s^2
An object with a mass of 10 kg sits on top of a bathroom scale inside an elevator. If the elevator begins to accelerate upward at a rate of 3 m / s2, what reading will the bathroom scale yield for the weight of the object? Use 9.8 m / s2 for the acceleration of gravity on the Earth’s surface.
128 N
If re is the radius of the Earth, how far above the surface of the Earth would you have to go so that your true weight is one-fourth of what it is on the surface of the Earth?
re
A hammer strikes a nail, driving it deep into a block of wood. The force on the nail by the hammer is represented by FNH. The force on the hammer by the nail is FHN. Which of the following correctly reflects what occurred when the hammer struck the nail?
FHN = -FNH
Which of the following correctly completes Newton’s third law? If object A exerts a force on object B, then object B always exerts a force back on A. The two forces are _____ in _____ but _____ in _____ to each other.
equal, magnitude, opposite, direction
In a particle accelerator, two particles collide head-on with each other. Their total masses are 1.67 × 10−27 kg and 9.1 × 10−31 kg. If the less massive one experiences an acceleration of 45 m / s2, what is the acceleration of the other particle?
0.025 m / s2
The force diagram shows a weight sitting motionless on a table. It has two forces acting upon it: the weight of the object pushing down and the force of the table pushing up. Given that the sum of the forces must equal zero, which of the following is correct?
FOT - mg = 0
The attached diagram shows a weight sitting motionless on a table.
It has three forces acting upon it. The first is the weight of the object pushing down (W); the second is the force of a man pushing down on it with his hand (FOM); the third is the force of the table pushing up (FOT). The sum of the three forces is zero, and can be expressed as the equation FOT + FOM + W = 0. Given that FOT is in the positive direction, which of the following correctly restates this equation as a vector equation and as a value for FOT?
FOT = -FOM - W FOT = FOM + mg
