(2.1 - 2.2) Forces
Unbalanced Forces are forces that are ________________ in magnitude and direction
not equal
What happens to friction when the roughness of a surface increases?
Friction increases
_______________ is always affected by gravity so it always changes wherever you are.
weight
Newton's First Law of Motion is the Law of Inertia. What are the 3 types of Inertia we learned about in class?
Inertia of Rest, Inertia of Motion, Inertia of Direction
What are the units for momentum?
kg x m/s
List the 7 examples/types of forces we went over in class.
Applied Force, Friction Force, Gravitational/Weight Force, Normal/Contact Force, Thrust Force, Drag Force, Tension Force
Name and rank the four types of friction from hardest to overcome to the easiest.
1. Static Friction
2. Kinetic/Sliding Friction
3. Rolling Friction
4. Fluid Friction
What are 2 factors that affect gravity?
1. Mass of the objects
2. Distance between the objects
Explain how inertia affects a passenger in a car that makes a sharp turn. What sensation do they experience?
If the car turns left, the body will "want" to move in the opposite direction
A 1.5 kg soccer ball has a momentum of 30 kg m/s after it was kicked. What was the ball's velocity?
v = 20 m/s
Explain the difference between balanced and unbalanced forces in your own words
Balanced forces have a net force of zero. Forces are equal in size and opposite in direction. No change in motion --> stays still, constant velocity (no acceleration)
Unbalanced Forces do not have a net force of zero. Forces are not equal in size and/or not opposite in direction. Change in motion --> changing velocity --> acceleration/deceleration
What are 2 factors that affect friction and explain why.
1. Surface Irregularities cause more resistance to motion. The microscopic bumps make it hard for objects to slide over each other.
2. Normal/Weight Force causes the irregularities between the surfaces to be pushed together, which causes more resistance to motion.
There is a common misconception when it comes to weight and how people portray it in real life. What is this misconception?
Most people say "My weight is X kg"
The correct statement should be "My mass is X kg" because the units for weight is newtons and the units for mass is kg.
Mathematically if the net force is 0, technically there is no change in motion. Does that mean Action-Reaction forces cancel out? Why or why not?
Action and Reaction forces don't cancel out because they act on different objects. Shooting a gun example.
What are the two types of collisions in momentum and what are their respective definitions?
Elastic Collision: The 2 objects remain separated after collision and momentum is conserved
Inelastic Collision: The 2 objects remain together after collision and momentum is conserved
A motorcycle is moving horizontally to the right with force of 600 N. The friction on the wheels opposes the motion with a force of 250 N to the left. There is an additional 75 N leftward force due to air resistance. What is the net force acting on the motorcycle?
275 N forward (right)
Why is pushing a cart full of students with wheels easier compared to a cart with no wheels?
A cart with no wheels slides across the ground. Sliding causes sliding friction, which is usually very large.
A cart with wheels rolls instead of slides. This produces rolling friction, which is much smaller than sliding friction.
If the distance between 2 objects is quadrupled (x4), and the mass of one of the objects is doubled (x2), how does the gravitational force between them change?
DOUBLE JEOPARDY
x1/8 (Reduces by x8)
Ms. Faith's Lamborghini is initially at rest then accelerates to a final velocity of 25 m/s to the right in 10 seconds. If a force of 5000 N is applied to achieve this acceleration, what is the mass of the car?
m = 2000 kg
A blue dodgeball of 2 kg is moving at 5 m/s and collides with a slightly bigger 3 kg yellow dodgeball that is initially at rest. The velocity after the collision of the blue ball is -1 m/s. What was the velocity of the yellow ball after the collision?
v = 4 m/s
A balloon is rising with a force of 40 N upward, while the weight of the balloon exerts a downward force of 60 N. Additionally, there is a 15 N rightward force due to the wind and a 10 N leftward force due to the balloon's drag.
Draw a FBD, calculate net force, state if the situation is a balanced or unbalanced forces and describe its motion.
check with moi
Why is fluid friction considered the weakest type of friction?
Because fluids have less direct surface-to-surface contact
Why does Earth's gravity have a stronger effect on you than the Sun's gravity, even though the Sun is much more massive? Incorporate Newton's Law of Universal Gravitation in your answer.
The distance has a bigger impact to the gravity than the mass because Newton's Law of Universal Gravitation states that the force is proportional to the PRODUCT of the masses but inversely proportional to the SQUARE of the distance.
Ms. Jean is piloting a helicopter with a mass of 4000 kg. The helicopter accelerates upwards at 2 m/s^2. The engine generates a thrust of 120,000 N. Calculate the force of air resistance (drag) acting against the helicopter.
Drag Force = 72760 N downwards
A 0.5 kg ball of clay is thrown at a stationary 2 kg block of wood. The clay sticks to the wood and they move together after the collision. If the velocity of the clay and wood is 2 m/s after the collision, what was the initial velocity of the clay?
v = 10 m/s