1 Kinematics and dynamics

Question 1

What is the pythagorean theorem?

Answer 1

A way to determine the magnitude of a resultant vector (the sum/differences of two or more vectors). This can be used when the tip-to-tail method of vector addition is not applicable and the vectors are in directions making a right angle.

Question 2

How do you use the right hand rule to combine a cross product resultant vector?

Answer 2

THe resultant of a cross product will always be perpendicular to the plane created by the two vectors.

For cross products and the right-hand rule, order matters! Unlike scalar multiplications, whish is commutative (3 x 4 = 4 x 3) vector multiplication is not commutative (A x B =/= B x A)!

Question 3

In vector calculus, how do you determine a cross product?

Answer 3

A x B = |A| |B| sinθ

Question 4

IN vector calculus, how do you determine the dot product of two vector quantities to generate a third vector or a scalar by multiplication?

Answer 4

A * B = |A| |B| cosθ

Question 5

give the equation for a newton (N), the SI unit for foce.

Answer 5

one killogram x metre / seconds squared

Question 6

What should you use as gravity in mcat calculations?

Answer 6

10 m/s²

Question 7

How does Newton’s third law relate to how the accelerations between the earth and you differ?

Answer 7

F = ma

Because the masses of a person and the earth are very different, the acceleration that each experience are also very different. The key to this is that according to Newton’s third law the force of gravity that the earth effects onto a person are the same as the ones a person exerts on the Earth.

Question 8

Give the equation for the magnitude of graviational forces between two objects.

Answer 8

Question 9

How does the gravitational force between you and something else differ if you get twice as far away from it.

Answer 9

It will be quartered

Question 10

What are the two types of friction?

Answer 10

statis friction (f_s): exists between a stationary object and the surface upon which it rests. The equation is f_s = u_sN (us is the static coefficient). To move the object N*u_s must be high enough to be greater than f_s

Kinetic friction (f_k) exists between a sliding object and the surface over which the object slides. f_k = u_kN

Question 11

When does a car tire experience kinetic and statis friction?

Answer 11

Kinetic: when sliding on ice or another slippery surface (eg. the material is sliding against another)

Static: during regular driving. The tire maintains an instantaneous point of static contact with the road and, therefore, experiences statis friction.

Question 12

Why is the coefficient of static friction always going to be more than the coefficient of kinetic friction?

Answer 12

It always requires more force to get an object to start sliding than it takes to keep an object sliding

Question 13

What is weight?

Answer 13

W (AKA F_g) = mg

where m is mass and g is gravitational force (round to 10 m/s²)

Question 14

Give the equation for average and instantaneous acceleration

Answer 14

Question 15

Give the following equations that pertain to linear motion and their angular counterparts:

• velocity
• acceleration
• displacement
• motion with time cancelled out

Answer 15

Question 16

How do you calculate forces when you have objects on a fictionless plane?

How do you calculate the normal force of the object?

Answer 16

m = mass

g = gravity (10 m/s²)

The normal force (the support force exerted upon an object that is in contact with another stable object - Newton’s third law) is mg cosθ

Question 17

How do you find the acceleration of an object on a frictionless incline?

Answer 17

F_net,parallel = F_g,parallel = ma_parallel

mgsinθ = ma_parallel

a_parallel = gsinθ

g = 10 m/s²

θ = the angle of the incline

Question 18

What keeps an object in uniform circular motion from breaking out of its circular pathway and moving in a linear direction (as it has a want to do due to inertia)?

Answer 18

Centripetal force. A force at a right angle to the direction of velocity at any given moment in uniform motion. It always points radially inward.

The equation for centripetal force is:

F_c = (mv²)/r

r = radius of circular path

Question 19

Give the full equation for torque

Answer 19

τ = r*F = rFsinθ

r = length of the lever arm (from fulcrum)

F = magnitude of the force

θ = angle between the lever arm and force vectors (usually 90 degrees, sin90 = 1)

Question 20

Is clockwise rotation caused by a postive torque or negative torque?

Answer 20

Negative

Positive torque generates counterclockwise rotation

Question 21

What measurement of mass is used in physics equations without conversion?

Answer 21

kilograms

Do not get this confused with chemistry where it is often grams