Physical Science

An object at rest cannot remain at rest unless which of the following holds? Hint 1for Part A. How to approach the problem This problem describes a situation of static equilibrium (i.e., a body that remains at rest). Hence, it is appropriate to apply Newton's 1st law. Hint 2for Part A. Newton's 1st law: a body at rest According to Newton's 1st law, a body at rest remains at rest if the net force acting on it is zero.

*The net force acting on it is zero The net force acting on it is constant and nonzero. The forces acting on it remain constant. There is only one force acting on it. Correct - If there is a net force acting on a body, regardless of whether it is a constant force, the body accelerates. If the body is at rest and the net force acting on it is zero, then it will remain at rest. The net force could be zero either because there are no forces acting on the body at all or because several forces are acting on the body but they all cancel out.

If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in

*a straight-line path. an inward spiral path. an outward spiral path. a curved path.

If both the forces acting on the object are horizontal and the 10-N force is directed to the right, while the 4-N force is directed to the left, the net force is horizontal and directed __________.

*cannot have a magnitude equal to 5N 5Ncannot have a magnitude equal to 10N 10Ncannot have the same direction as the force with magnitude 10N 10Nmust have a magnitude greater than 10N

If both the forces acting on the object are horizontal and the 10-N force is directed to the right, while the 4-N force is directed to the left, the net force is horizontal and directed __________.

*in the same direction as the 10-N force in the opposite direction to the 10-N force

An object in motion tends to remain in motion

*without the need of a force. only when an external force acts on it. because of a force inside the object. due to their nature.

The net force on any object moving at constant velocity is

*zero. 10 meters per second squared. equal to its weight less than its weight.

In the textbook we learn that the cause of acceleration is given by Newton's second law: a=Fnet/m Find the acceleration that can result from a net force of 14 N exerted on a 3.4-kg cart. (Note: The unit N/kg is equivalent to m/s2)

4.1 m/s2

A rocket of mass 140000 kg undergoes an acceleration of 1.2 m/s2 Find the net force acting on it.

Fnet = 1.7×10^5 N

A simple rearrangement of Newton's second law gives Fnet=ma Find a net force that is needed to give a 7.0-kg package an acceleration of 6.8 m/s2 (Note: The units kg⋅m/s2 and N are equivalent.).

Fnet = 48 N

Two forces, of magnitude 4N4N and 10N10N, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object Hint 1for Part E. How to approach the problem By definition, the net force is the vector sum of all forces acting on the object. To find the magnitude of the net force you need to add the components of the two forces acting. Try adding the two forces graphically (by connecting the head of one force to the tail of the other). The directions of the two forces are arbitrary, but by trying different possibilities you should be able to determine the maximum and minimum net forces that could act on the object. Hint 2for Part E. Find the net force when the two forces act on the object in opposite directions Find the magnitude of the net force if both the forces acting on the object are horizontal and the 10-N force is directed to the right, while the 4-N force is directed to the left.

Hint 1for Part 2. Vector addition The magnitude of the vector sum of two parallel forces is the sum of the magnitudes of the forces. The magnitude of the vector sum of two antiparallel forces is the absolute value of the difference in magnitudes of the forces. ANSWER: 6.0N

A block of mass 2kg2kg is acted upon by two forces: 3N3N (directed to the left) and 4N4N (directed to the right). What can you say about the block's motion? Hint 1for Part C. How to approach the problem This problem describes a situation of dynamic motion (i.e., a body that is acted on by a net force). Hence, it is appropriate to apply Newton's 2nd law, which allows you to relate the net force acting on a body to the acceleration of the body. Hint 2for Part C. Newton's 2nd law Newton's 2nd law states that a body accelerates if a net force acts on it. The net force is proportional to the acceleration of the body and the constant of proportionality is equal to the mass of the body. In other words, F=ma, where F is the net force acting on the body, and m and a are the mass and the acceleration of the body, respectively. Hint 3for Part C. Relating acceleration to velocity Acceleration is defined as the change in velocity per unit time. Keep in mind that both acceleration and velocity are vector quantities.

It must be moving to the left. It must be moving to the right. It must be at rest. *It could be moving to the left, moving to the right, or be instantaneously at rest. Correct The acceleration of an object tells you nothing about its velocity, which is the direction and speed at which it is moving. In this case, the net force on (and therefore the acceleration of) the block is to the right, but the block could be moving left, right, or in any other direction. The block could also be instantaneously at rest, because a zero velocity again implies nothing about the acceleration.

Consider a 100-kgkg box of tools in locations A, B, and C. Part A Rank from greatest to least the masses of the 100-kgkg box of tools.

Rank from greatest to least. To rank items as equivalent, overlap them. *All Equal

Part B Rank from greatest to least the weights of the 100-kgkg box of tools.

Rank from greatest to least. To rank items as equivalent, overlap them. *Jupiter, Earth Moon

If a block is moving to the left at a constant velocity, what can one conclude? Hint 1for Part B. How to approach the problem This problem describes a situation of dynamic equilibrium (i.e., a body that moves at a constant velocity). Hence, it is appropriate to apply Newton's 1st law. Hint 2for Part B. Newton's 1st law: a body in motion According to Newton's 1st law, a body initially in motion continues to move with constant velocity if the net force acting on it is zero.

There is exactly one force applied to the block. The net force applied to the block is directed to the left. *The net force applied to the block is zero. There must be no forces at all applied to the block Correct If there is a net force acting on a body, regardless of whether the body is already moving, the body accelerates. If a body is moving with constant velocity, then it is not accelerating and the net force acting on it is zero. The net force could be zero either because there are no forces acting on the body at all or because several forces are acting on the body but they all cancel out.

Consider the video demonstration that you just watched. Which of the following changes would make it more likely for the ball to hit both the white can and the green can?

Use a ball that is lighter than the original ball, but still heavier than an empty can. Roll the ball faster. Roll the ball slower. Use a ball that is heavier than the original ball. *None of the above (By Newton's first law, after it has left the circular track, the ball will travel in a straight line until it is subject to a nonzero net force. Thus, the ball can only hit the white can, because that is the only can in the ball's straight-line path.)

An astronaut of mass 135 kg recedes from her spacecraft by activating a small propulsion unit attached to her back. The force generated by a spurt is 20 N Find her acceleration.

a = 0.15 ms2

In the textbook acceleration is defined as a=Δv/Δt. Use this formula to find the acceleration of a cart on an inclined plane that gains 6.2 m/s each 1.0 s .

a = 6.2 m/s2

A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be __________. Hint 1for Part D. How to approach the problem This problem describes a situation of dynamic motion (i.e., a body that is acted on by a net force). Hence, it is appropriate to apply Newton's 2nd law, which allows you to relate the net force acting on a body to the acceleration of the body. Hint 2for Part D. Newton's 2nd law Newton's 2nd law states that a body accelerates if a net force acts on it. The net force is proportional to the acceleration of the body and the constant of proportionality is equal to the mass of the body. In other words, F=ma, where F is the net force acting on the body, and m and a are the mass and the acceleration of the body, respectively.

continuously changing direction moving at constant velocity *moving with a constant nonzero acceleration moving with continuously increasing acceleration Correct Since there is a net force acting, the body does not move at a constant velocity, but it accelerates instead. However, the force acting on the body is constant. Hence, according to Newton's 2nd law of motion, the acceleration of the body is also constant.

A space probe in remote outer space continues moving

in a curved path. because some kind of force acts on it. *even though no force acts on it. due to gravity.