Newton and his laws

Question 1

True or false: Two objects exerting an equal and opposite force on each other will experience the same magnitude of acceleration because force and acceleration are directly proportional.

Answer 1

This statement is false. Two objects exerting equal and opposite forces on each other will experience different accelerations if their masses are different. This concept is represented by Newton’s second law- Force=(mass)(acceleration). The acceleration will only be the same if the masses are equal. Because this question stem does not specify what the mass of each object is, we cannot assume that the acceleration will be equal.

Question 2

What are the four fundamental forces?

Answer 2

Gravitational Electromagnetic Weak nuclear Strong nuclear

Question 3

Newtons 1st law

Answer 3

The law of inertia, an object in motion will stay in motion and an object at rest will stay at rest unless acted upon by a force. The larger the mass, the larger the inertia. This is why it takes a greater force to move an elephant than a mouse. The elephant has a larger inertia.

Question 4

Newtons 2nd law

Answer 4

Fnet=ma

Question 5

Newtons 3rd law

Answer 5

Fab=Fba, every action has an equal and opposite reaction

Question 6

What is a conservative force?

Answer 6

A force independent of path that is concerned with beginning and end product.

Question 7

What is a nonconservative force?

Answer 7

A path dependent force (that can dissipate energy sometimes along the way)

Question 8

What are some examples of conservative forces?

Answer 8

Gravity, Electrostatic, Magnetic, Spring, general push/pull

Question 9

What are some examples of nonconservative forces?

Answer 9

Friction, air resistance, viscosity

Question 10

Gravitational force equations

Answer 10

F=mg, and F=(GmM)/r^2

Question 11

Electrostatic force equations

Answer 11

F=qE, and coulumbs law F=kqQ/r^2

Question 12

Magnetic force equations

Answer 12

F=iLBsintheta, F=qvBsintheta

Question 13

Spring force equations

Answer 13

Hooks law F=kdeltax

Question 14

What are the units for force?

Answer 14

Newtons= 1kg*m/s^2

Question 15

Hooks law

Answer 15

Describes the force associated with Springs: F=kΔX

Question 16

Coulumb’s Law

Answer 16

Describes the force between two charges: F=kQq/r^2

Question 17

Force of friction

Answer 17

Ffric=μN

Question 18

Force of Air Resistance/ Fdrag

Answer 18

Fdrag= 1/2 p v^2 Cd A

Question 19

True or False: The only force acting on a projectile in motion is in the y direction

Answer 19

True- the only force acting on a projectile is gravity

Question 20

What would the graph look like if you applied a force to a heavy box until it moved

Answer 20

Question 21

What are the components of a block on an inclined plane with friction?

Answer 21

Fnormal= mgcostheta

Fgravity= mgsintheta

Ffric=umgcostheta

Question 22

Assume that Team 1 pulls with a force of 100 N and Team 2 pulls with a force of 100 N. What is the tension in the rope?

Answer 22

There is a force balance between the two teams in this case. So long as there is a force balance between the two teams, no individual team will fall forward, and the tension in the rope will adopt the force value being applied by an individual team. This is because the tension force is best thought of as the force exerted by the rope on each team, which can be expressed as pairs of action-reaction forces according to Newton’s third law. The harder the teams pull, while maintaining equal forces, the greater the tension will be in the rope. In this case, the two teams are both pulling with 100 N of force, and thus the tension in the rope will be 100 N.

Question 23

A 95 kg patient with a prosthetic limb is standing up at rest on a 10° grade wet road. For the patient not to slip, what is the minimum friction needed?

Answer 23

162 N

A force body diagram shows that the weight vector is divided into two components, one parallel to the road (weight × sin 10°) and one perpendicular to the road (weight × cos 10°). Since the person is at rest, the parallel component of the weight is balanced by the force of friction, so they have the same value (but opposite direction). Friction = (95 kg)(9.8 m/s2)(sin 10°) = 162 N. The MCAT will not expect you to know the sine of 10° specifically, but we should know that sin 0° = 0 and that sin 30° = 0.5, so we can estimate that sin 10° will be fairly low – an approximation of it between 0.1 and 0.2 will do.