Question 1

A 160 lb person has a mass of 160/32 = 5 slugs.A 160-lb person steps into an elevator and stands on a bathroom scale.Determine the scale reading for the given scenarios. -The elevator is accelerating upwards at 2 ft/s².

Accepted Answer

When the elevator accelerates upwards, the apparent weight increases. The apparent weight is calculated by adding the product of mass and acceleration to the actual weight. Here, the apparent weight is 160 lb + (5 slugs * 2 ft/s²) = 170 lb.

Question 2

You whirl a 2-kg body attached to a 1-meter cord around your head in a nearly horizontal circle with a speed of 4 m/s.The tension in the cord is

Accepted Answer

The tension in the cord is the centripetal force required to keep the body moving in a circle. The formula for centripetal force is F = mv²/r. Substituting the given values: F = (2 kg)(4 m/s)²/(1 m) = 32 N.

Question 3

Two forces of 4 N and 12 N act on a body simultaneously.The net force on the body is

Accepted Answer

The net force depends on the direction of the forces, which is not provided.

Question 4

Which is larger,a newton or a pound?

Accepted Answer

A pound is larger than a newton. 1 pound-force is approximately equal to 4.44822 newtons.

Question 5

The force needed to make an object move in a circle is

Accepted Answer

The force needed to make an object move in a circle is known as centripetal force. This force acts towards the center of the circle and is required to keep the object moving in a circular path. Without the centripetal force, the object would move in a straight line tangent to the circle.

Question 6

If object A has more mass than object B,

Accepted Answer

All statements are correct: A will weigh more due to greater mass, will require more force to accelerate, and will have more inertia, making it harder to maintain circular motion.

Question 7

When a freely falling object reaches its terminal speed,

Accepted Answer

When a freely falling object reaches its terminal speed, it means that the air resistance acting on the object is equal to the gravitational force. This balance of forces causes the net force to be zero, resulting in zero acceleration. Therefore, choice B is the correct answer.

Question 8

The force that keeps your feet from sliding as you walk is

Accepted Answer

The force that keeps your feet from sliding as you walk is static friction. Kinetic friction is the force that resists motion when two surfaces are already in motion relative to each other. Centripetal force is the force that keeps an object moving in a circular path, and weight is a force caused by gravity. None of these forces are directly related to keeping your feet from sliding as you walk.

Question 9

A 160 lb person has a mass of 160/32 = 5 slugs.A 160-lb person steps into an elevator and stands on a bathroom scale.Determine the scale reading for the given scenarios.
-The elevator accelerates upwards and is now moving at a constant speed.

Accepted Answer

When the elevator moves at a constant speed, there is no net acceleration acting on the person. Therefore, the scale reads the actual weight of the person, which is 160 lb.

Question 10

A car moving at a constant speed goes around a curve of 400-ft radius and then goes around a second curve of 200-ft radius.The centripetal force acting on the car as it goes around the 200-ft radius curve is ___________ the value of the centripetal force acting on the car as it goes around the 400-ft radius curve.

Accepted Answer

The centripetal force is directly proportional to the square of the velocity and inversely proportional to the radius of the curve. At a constant speed, the velocity will be the same for both curves. Therefore, the centripetal force will be inversely proportional to the radius. The centripetal force is proportional to 1/radius². So, the ratio of the forces will be (1/400²)/(1/200²), which simplifies to 1/4 or 0.25. This means that the force on the 200-ft radius curve is four times greater than the force on the 400-ft radius curve, or twice as much as in answer choice D. However, since this question asks for the ratio between them, the best choice is D.

Question 11

If the net force on an object is zero,

Accepted Answer

If the net force on an object is zero, it means that the sum of all the forces acting on the object is zero. In such a case, the object may be in motion, but its acceleration must be zero. This means that the object will either remain at rest or continue to move with a constant velocity (in a straight line), but it will not change its speed or direction. Therefore, options A, B, and D do not necessarily apply.

Question 12

The SI units of acceleration are

Accepted Answer

The SI unit of acceleration is meters per second squared (m/s²).

Question 13

You push on a block on frictionless ice with a force of 8 N,causing it to accelerate at 2 m/s².The mass of the block is

Accepted Answer

We know that force (F) is related to the mass (m) and acceleration (a) through the equation:

F = ma

In this problem, we are given F = 8 N and a = 2 m/s^2. 
To find the mass, we can rearrange the equation as:

m = F/a

Plugging in the values we get:

m = 8 N / 2 m/s^2 
m = 4 kg

Therefore, the mass of the block is 4 kg, which corresponds to option B).

Question 14

An example of an action at a distance force is

Accepted Answer

The answer of An example of an action at a...

Question 15

The frequency of a body oscillating from a spring on the Moon is___________ the frequency of the same body oscillating from the same spring on Earth.

Accepted Answer

The frequency of an oscillating body from a spring depends only on the mass of the object and the spring constant, which remain constant on both Earth and Moon. Therefore, the frequency of oscillation will be the same on both Earth and Moon.

Question 16

The acceleration of a body is

Accepted Answer

According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Therefore, the direction of acceleration is in the same direction as the net force acting on the object, which is option B. The direction of acceleration may or may not be the same as the direction of velocity or the direction in which the body is moving.

Question 17

The SI units of velocity are

Accepted Answer

Velocity is defined as the rate of change of displacement with time. SI unit of displacement is meter (m) and the unit of time is second (s). Therefore, the SI unit of velocity is meters per second (m/s). Option D is the only one that represents this unit. All the other options represent velocity in miles per hour or kilometers per hour which are not SI units.

Question 18

You roll a ball off a table and at the same time drop a second ball straight down from the edge of table.The second ball reaches the ground ____________ the first ball reaches the ground.

Accepted Answer

Both balls will reach the ground at the same time regardless of their masses because they are both affected by the same acceleration due to gravity. This is known as the principle of equivalence.

Question 19

Two identical cars are traveling around the same curve on a highway.One of them is moving at 60 mph,and the other is moving at 30 mph.The centripetal force acting on the car moving at 60 mph is __________ the value of the centripetal force acting on the car moving at 30 mph.

Accepted Answer

The centripetal force is proportional to the square of the velocity. Therefore, if the speed doubles, the centripetal force increases by a factor of four.

Question 20

Starting from rest,a 2-kg body acquires a speed of 8 m/s in 2 seconds.The net force acting on the body is

Accepted Answer

The net force acting on the body is equal to the mass of the body multiplied by its acceleration. In this case, the mass of the body is 2 kg and its acceleration is 8 m/s^2. Therefore, the net force acting on the body is 2 kg * 8 m/s^2 = 16 N.

Quiz 2: Newtons Laws

A 160 lb person has a mass of 160/32 = 5 slugs.A 160-lb person steps into an elevator and stands on a bathroom scale.Determine the scale reading for the given scenarios. -The elevator is accelerating upwards at 2 ft/s2.