Question 1

A barefoot field-goal kicker imparts a speed of 25 m/s to a football at rest.If the football has a mass of 0.50 kg and time of contact with the football is 0.020 s,what is the force exerted on the foot?

Accepted Answer

We can use the impulse-momentum theorem to solve this problem.

Impulse = Change in momentum

The initial momentum of the football is zero (since it's at rest). The final momentum can be calculated using the mass of the football (0.50 kg) and the speed imparted by the kicker (25 m/s):

Final momentum = (0.50 kg)(25 m/s) = 12.5 kg*m/s

Therefore, the impulse is:

Impulse = Final momentum - Initial momentum 
Impulse = 12.5 kg*m/s - 0 kg*m/s 
Impulse = 12.5 kg*m/s

The impulse is equal to the force (F) multiplied by the time of contact (t):

Impulse = F*t

Therefore, we can solve for the force:

F = Impulse / t 
F = (12.5 kg*m/s) / (0.020 s) 
F = 625 N

Therefore, the force exerted on the foot is 625 N, which is choice C.

Question 2

A rock is rolled in the sand.It starts at 6.0 m/s,moves in a straight line for a distance of 4.5 m,and then stops.What is the magnitude of the average acceleration?

Accepted Answer

B

Question 3

A 1,500-kg sailboat experiences an eastward force of 3,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W).What is the magnitude of the resultant acceleration?

Accepted Answer

The eastward component of the wind force is 6000cos45° = 4243 N. The resultant force is therefore 3500 N + 4243 N = 7743 N eastward. The magnitude of the acceleration is therefore 7743 N / 1500 kg = 5.16 m/s2.

Question 4

The accelerating force of the wind on a small 150-kg sailboat is 756 N northeast.If the drag of the keel is 535 N acting west,what is the acceleration of the boat?

Accepted Answer

The answer of The accelerating force of the wind on...

Question 5

A 9.0-kg bowling ball experiences a net force of 6.0 N.What will be its acceleration?

Accepted Answer

The equation for Newton's Second Law is F = ma, where F is the net force acting on an object, m is the mass of the object, and a is the acceleration of the object. Rearranging this equation, we get a = F/m.

In this problem, we are given F = 6.0 N and m = 9.0 kg. Substituting these values into the equation above, we get:

a = F/m = 6.0 N / 9.0 kg = 0.67 m/s^2

Therefore, the acceleration of the bowling ball is 0.67 m/s^2, which corresponds to choice (D).

Question 6

A 2,000-kg sailboat experiences an eastward force of 2,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W).What is the direction of the resultant acceleration?

Accepted Answer

First, we need to find the vector sum of the two forces acting on the sailboat. To do this, we can break the wind force into its x and y components:
Fx = - 6000 cos(45°) = -4243 N (westward)
Fy = 6000 sin(45°) = 4243 N (northward)
Next, we can add up the x and y components of all the forces acting on the sailboat:
ΣFx = -4243 N + 0 N = -4243 N (westward)
ΣFy = 2500 N + 4243 N = 6743 N (northward)
Now we can use the Pythagorean theorem to find the magnitude of the resultant force:
FR = sqrt((-4243 N)^2 + (6743 N)^2) = 7977 N
Finally, we can use the inverse tangent function to find the direction of the resultant force:
θ = tan^-1(6743 N / 4243 N) = 60.11°
Since the northward force is greater than the westward force, the direction of the resultant force will be slightly north of east. D is the closest answer choice to this direction.

Question 7

If we know an object is moving at constant velocity,we may assume:

Accepted Answer

When an object is moving at a constant velocity, its acceleration is zero. This means that the net force acting on the object must also be zero according to Newton's second law (F net = ma). Therefore, choice A is the correct assumption to make.

Question 8

What condition must apply to a system's state of motion for it to be regarded as an inertial frame of reference?

Accepted Answer

An inertial frame of reference is one in which an object remains at rest or in constant velocity unless acted upon by an external force. Thus, a system's state of motion must be in constant velocity to be regarded as an inertial frame of reference. Choices A, C, and D do not fit this condition.

Question 9

Two ropes are attached to a 35-kg object.The first rope applies a force of 20 N and the second,55 N.If the two ropes are perpendicular to each other,what is the resultant acceleration of the object?

Accepted Answer

The answer of Two ropes are attached to a 35-kg...

Question 10

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.An astronaut's life support backpack weighs 350 lb on Earth.What does it weigh on the Moon?

Accepted Answer

The weight of the backpack on the Moon would be one-sixth of its weight on Earth. Therefore,
Weight on Moon = Weight on Earth/6
Weight on Moon = 350/6
Weight on Moon = 58 lb (rounded to the nearest whole number)

Question 11

Rita accelerates a 0.45-kg ball from rest to 8.0 m/s during the 0.15 s in which her foot is in contact with the ball.What average force does she apply to the ball during the kick?

Accepted Answer

The answer of Rita accelerates a 0.45-kg ball from rest...

Question 12

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.What net force would be required to accelerate a 15-kg object at 8.0 m/s² on the moon?

Accepted Answer

The weight (mg) of the object on the moon would be 1/6th of its weight on Earth. Therefore, mg on the moon = (15 kg) x (1/6) x (9.8 m/s^2) = 24.5 N
To accelerate the object at 8.0 m/s^2, we need to apply a net force F = ma, where m = 15 kg and a = 8.0 m/s^2. Therefore, F = (15 kg) x (8.0 m/s^2) = 120 N
So the net force required to accelerate the object at 8.0 m/s^2 on the moon is 120 N.

Therefore, the correct answer is D.

Question 13

If we know that a nonzero net force is acting on an object,which of the following must we assume regarding the object's condition? The object is:

Accepted Answer

If a nonzero net force is acting on an object, we must assume that the object is being accelerated. This is because Newton's second law states that force is directly proportional to acceleration, and a nonzero net force means there is an unbalanced force acting on the object, causing a change in its velocity. The object could be moving with a constant velocity only if the net force acting on it is zero (according to Newton's first law). There is no reason to assume that the object is at rest or losing mass based solely on the knowledge that a nonzero net force is acting on it.

Question 14

An automobile of mass 3,000 kg moving at 45 m/s is braked suddenly with a constant braking force of 9,000 N.How far does the car travel before stopping?

Accepted Answer

The correct answer is B because the car travels 338 m before stopping. The formula for the distance traveled by a car before stopping is:d = (v^2) / (2 * a)where:d is the distance traveled (in meters)v is the initial velocity (in meters per second)a is the acceleration (in meters per second squared)In this case, the initial velocity is 45 m/s, the acceleration is -9,000 N / 3,000 kg = -3 m/s^2, and the distance traveled is:d = (45 m/s)^2 / (2 * -3 m/s^2) = 338 m

Question 15

An astronaut applies a force of 450 N to an asteroid,and it accelerates at 9.00 m/s².What is the asteroid's mass?

Accepted Answer

The mass of the asteroid can be calculated using Newton's second law, F = ma. Rearranging gives m = F/a = 450 N / 9.00 m/s² = 50 kg.

Question 16

Which of the following expresses a principle,which was initially stated by Galileo and was later incorporated into Newton's laws of motion?

Accepted Answer

The principle that the natural condition for a moving object is to remain in motion, also known as the law of inertia, was initially stated by Galileo and later incorporated into Newton's first law of motion. Choice A is an expression of Newton's second law, while choice B is an expression of Newton's third law. Choice D is not a valid principle of motion.

Question 17

Two forces act on a 5.00-kg object.One of the forces is 11.0 N.If the object accelerates at 4.00 m/s²,what is the greatest possible magnitude of the other force?

Accepted Answer

The net force on the object is given by F_net = mass * acceleration = 5.00 kg * 4.00 m/s² = 20.0 N. If one force is 11.0 N, the greatest possible magnitude of the other force occurs when the forces are in the same direction, so the other force is 20.0 N - 11.0 N = 9.0 N. However, this is incorrect. The correct calculation should consider the forces in opposite directions, so the other force is 20.0 N + 11.0 N = 31.0 N.

Question 18

Which of the following is an example of the type of force that acts at a distance?

Accepted Answer

Gravitational, magnetic, and electrical forces are all examples of forces that act at a distance. They do not require physical contact between two objects to exert a force on one another. Instead, they are mediated by fields (such as a gravitational field, magnetic field, or electric field) that exist around objects that have mass, electric charge, or magnetic properties.

Question 19

A cart of weight 25 N is accelerated across a level surface at 0.15 m/s².What net force acts on the wagon? (g = 9.8 m/s²)

Accepted Answer

The answer of A cart of weight 25 N is...

Question 20

A 60.0-kg man jumps 1.00 m down onto a concrete walkway.His downward motion stops in 0.0400 seconds.If he forgets to bend his knees,what force is transmitted to his leg bones?

Accepted Answer

The force can be calculated using the impulse-momentum theorem. The change in momentum is equal to the impulse, which is the force times the time interval. The velocity just before impact can be found using the equation for free fall: v = sqrt(2gh). Then, using F = Δp/Δt, where Δp is the change in momentum (mass times change in velocity), we find the force to be approximately 6,600 N.

Quiz 4: The Laws of Motion

A barefoot field-goal kicker imparts a speed of 25 m/s to a football at rest.If the football has a mass of 0.50 kg and time of contact with the football is 0.020 s,what is the force exerted on the foot?

A rock is rolled in the sand.It starts at 6.0 m/s,moves in a straight line for a distance of 4.5 m,and then stops.What is the magnitude of the average acceleration?

A 1,500-kg sailboat experiences an eastward force of 3,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W) .What is the magnitude of the resultant acceleration?

The accelerating force of the wind on a small 150-kg sailboat is 756 N northeast.If the drag of the keel is 535 N acting west,what is the acceleration of the boat?

A 9.0-kg bowling ball experiences a net force of 6.0 N.What will be its acceleration?

A 2,000-kg sailboat experiences an eastward force of 2,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W) .What is the direction of the resultant acceleration?

If we know an object is moving at constant velocity,we may assume:

What condition must apply to a system's state of motion for it to be regarded as an inertial frame of reference?

Two ropes are attached to a 35-kg object.The first rope applies a force of 20 N and the second,55 N.If the two ropes are perpendicular to each other,what is the resultant acceleration of the object?

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.An astronaut's life support backpack weighs 350 lb on Earth.What does it weigh on the Moon?

Rita accelerates a 0.45-kg ball from rest to 8.0 m/s during the 0.15 s in which her foot is in contact with the ball.What average force does she apply to the ball during the kick?

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.What net force would be required to accelerate a 15-kg object at 8.0 m/s² on the moon?

If we know that a nonzero net force is acting on an object,which of the following must we assume regarding the object's condition? The object is:

An automobile of mass 3,000 kg moving at 45 m/s is braked suddenly with a constant braking force of 9,000 N.How far does the car travel before stopping?

An astronaut applies a force of 450 N to an asteroid,and it accelerates at 9.00 m/s².What is the asteroid's mass?

Which of the following expresses a principle,which was initially stated by Galileo and was later incorporated into Newton's laws of motion?

Two forces act on a 5.00-kg object.One of the forces is 11.0 N.If the object accelerates at 4.00 m/s²,what is the greatest possible magnitude of the other force?

Which of the following is an example of the type of force that acts at a distance?

A cart of weight 25 N is accelerated across a level surface at 0.15 m/s².What net force acts on the wagon? (g = 9.8 m/s²)

A 60.0-kg man jumps 1.00 m down onto a concrete walkway.His downward motion stops in 0.0400 seconds.If he forgets to bend his knees,what force is transmitted to his leg bones?

Quiz 4: The Laws of Motion

A barefoot field-goal kicker imparts a speed of 25 m/s to a football at rest.If the football has a mass of 0.50 kg and time of contact with the football is 0.020 s,what is the force exerted on the foot?

A rock is rolled in the sand.It starts at 6.0 m/s,moves in a straight line for a distance of 4.5 m,and then stops.What is the magnitude of the average acceleration?

A 1,500-kg sailboat experiences an eastward force of 3,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W) .What is the magnitude of the resultant acceleration?

The accelerating force of the wind on a small 150-kg sailboat is 756 N northeast.If the drag of the keel is 535 N acting west,what is the acceleration of the boat?

A 9.0-kg bowling ball experiences a net force of 6.0 N.What will be its acceleration?

A 2,000-kg sailboat experiences an eastward force of 2,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W) .What is the direction of the resultant acceleration?

If we know an object is moving at constant velocity,we may assume:

What condition must apply to a system's state of motion for it to be regarded as an inertial frame of reference?

Two ropes are attached to a 35-kg object.The first rope applies a force of 20 N and the second,55 N.If the two ropes are perpendicular to each other,what is the resultant acceleration of the object?

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.An astronaut's life support backpack weighs 350 lb on Earth.What does it weigh on the Moon?

Rita accelerates a 0.45-kg ball from rest to 8.0 m/s during the 0.15 s in which her foot is in contact with the ball.What average force does she apply to the ball during the kick?

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.What net force would be required to accelerate a 15-kg object at 8.0 m/s2 on the moon?

If we know that a nonzero net force is acting on an object,which of the following must we assume regarding the object's condition? The object is:

An automobile of mass 3,000 kg moving at 45 m/s is braked suddenly with a constant braking force of 9,000 N.How far does the car travel before stopping?

An astronaut applies a force of 450 N to an asteroid,and it accelerates at 9.00 m/s2.What is the asteroid's mass?

Which of the following expresses a principle,which was initially stated by Galileo and was later incorporated into Newton's laws of motion?

Two forces act on a 5.00-kg object.One of the forces is 11.0 N.If the object accelerates at 4.00 m/s2,what is the greatest possible magnitude of the other force?

Which of the following is an example of the type of force that acts at a distance?

A cart of weight 25 N is accelerated across a level surface at 0.15 m/s2.What net force acts on the wagon? (g = 9.8 m/s2)

A 60.0-kg man jumps 1.00 m down onto a concrete walkway.His downward motion stops in 0.0400 seconds.If he forgets to bend his knees,what force is transmitted to his leg bones?

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.What net force would be required to accelerate a 15-kg object at 8.0 m/s² on the moon?

An astronaut applies a force of 450 N to an asteroid,and it accelerates at 9.00 m/s².What is the asteroid's mass?

Two forces act on a 5.00-kg object.One of the forces is 11.0 N.If the object accelerates at 4.00 m/s²,what is the greatest possible magnitude of the other force?

A cart of weight 25 N is accelerated across a level surface at 0.15 m/s².What net force acts on the wagon? (g = 9.8 m/s²)