Motion And Force

Question 1

What is the best physical equation to use for linear motion problems when velocity is unknown?

Answer 1

\delta x = v_0 t + (1/2) a t^2

This will assume constant acceleration

Question 2

What is the best equation to use for linear motion problems when you don’t know displacement?

Answer 2

v - v_0 = at

This will assume constant acceleration

Question 3

What is the best equation to use for linear motion when you don’t know time (t)?

Answer 3

v^2 = v_0^2 + 2a (x - x_0)

This will assume constant acceleration

Question 4

What is average velocity in a uniformly accelerated motion problem?

Answer 4

V_avg = (1/2) (v + v_0)

Question 5

What does a flat line, positive sloped line, and negative slope line mean on a displacement vs. time graph?

Answer 5

Flat line means no movement or change in distance / displacement
Positive sloped line means velocity in positive direction
Negative sloped line means velocity in negative direction
Area under the curve has no significance

Question 6

What does a constant line, positive sloped line, and negative sloped line mean in a velocity vs. time graph?

Answer 6

Constant line means no change in velocity, but depending on where it is it could mean positive, 0, or negative velocity
Positive sloped line means acceleration in positive direction; if below the x-axis then slowing down, if above x-axis then speeding up
Negative sloped line means acceleration in negative direction; if below the x-axis then speeding up, if above x-axis then slowing down
Signed area under curve is displacement, non-signed area under curve is distance traveled

Question 7

In projectile motion, what determines the time until an object hits the ground?

Answer 7

Only the initial vertical velocity
If two objects with the same initial vertical velocity (and same initial height) have different horizontal velocities, they will land on the ground at the same time
In order to find time, just use the y equation component to determine when the object hits the ground as if it was just thrown straight up in the air, and then compute the distance traveled using that time

Question 8

Inertia

Answer 8

Tendency of all objects to remain in present state of motion
Mass is quantitative measure of object’s inertia, where mass indicates quantitatively how much object will resist change in motion

Question 9

Weight

Answer 9

Gravitational force that object experiences when close to much larger body, like Earth
Measured in Newtons (N)
Equal to mg

Question 10

Center of mass

Answer 10

Single point at which all of the system’s mass can be considered to be concentrated
Point through which a single force can be applied in any direction to cause all points in system to accelerate equally
If force applied to object beyond center of mass object will rotate, because force will generate torque

Question 11

What are the four types of forces in nature?

Answer 11

1. Strong nuclear force
2. Weak nuclear force
3. Gravitational force
4. Electromagnetic force

Question 12

What equation should you use for a parabolic motion problem?

Answer 12

V = sqrt(2gh)

When v_0 is 0

Question 13

What is the equation for gravitational force?

Answer 13

F = G (m1 m2 / r^2)

Question 14

Frictional Force

Answer 14

Static: fs <= /mu_s F_n
Kinetic: fk = /mu_k Fn
Contiguous surfaces may exert equal and opposite forces against each other parallel to their contiguous surfaces
If surfaces do not slide relative to each other, then static
If surface slide relative to one another, then kinetic