Describing Motion & Force
What is the difference between a contact force and a noncontact force?
A contact force involves a force between two objects in contact.
For example, friction between your feet and the ground can be present.
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A non-contact force involves a force between objects not touching. You can't 'see' anything physically touching, but there is still an attraction or repulsion.
For example, magnetic forces between two magnets can happen when the magnets are near but not touching
How do you calculate speed?
Speed = Distance
_______
time
how do you calculate acceleration?
acceleration = force / mass
what are the 4 different types of friction
1. static
2. rolling
3. sliding
4. fluid
what is accelerated speed?
acceleration
True or False
Objects that are fixed to Earth—such as a tree, a stop sign, or a building—make good reference points.
True
A reference point is a place or object used for comparison to determine whether something is in motion.
An object is in motion if its position changes when compared to another object.
If a runner completes a 12-kilometer race in 1.5 hours, what is the runner's speed?
8 kilometers per hour
A 124-N net force acts on a 8-kg jug of water. What is the resulting acceleration of the jug?
15.5
what factors affect friction
- type of surface
- force applied
what is directional speed?
velocity
If two objects are pushed with the same force, but one object has more mass, what will be the result?
The object with less mass will accelerate more
What are the 4 different types of speed?
1. instantaneous
2. average
3. directional
4. average
You push your younger sister on a swing in a park. Then you give her a harder push. Explain what happens in each case, in terms of the second and third laws of motion.
2nd law - more force applied, increase in acceleration
3rd law - when I push harder going to the right, my body reacts by moving backwards once I push off of her
what factors affect gravitational attraction
- mass
- distance
If a mouse is being chased by a cat how can the cat use velocity to escape the cat?
it can both increase speed and change direction
OR
it can run at the same speed but change direction
OR
it can run in the same direction but increase its speed
If a car is moving at a constant speed and you are standing still, what is your reference point?
a. The car's speedometer b. The car's engine
c. Your location on the road
d. The color of the car
c. Your location on the road
What is the speed of a body which is gathered in a relatively shorter period of time Or in an instance is known as instantaneous speed of a body.
instantaneous speed
what is inertia
a tendency not to move or change unless acted on by some external force
what is the difference between mass and weight
Mass is the total amount of matter, or "stuff," in an object. Weight is the force of gravity on an object.
which one of newton's laws of motion is the law of inertia
Newton's 1st Law of Motion
If a bus passes a streetlight, how do you know the bus is in motion relative to the streetlight?
The streetlight appears to move in the opposite direction
______ speed is the total distance covered in a specific time interval. For example:- A bus travels 65 km in the time span of 1hr ,
Average
what are newton's three laws of motion
1. objects at rest stay at rest.. objects in motion stay in motion. unless a force is applied
2. objects with more mass need more force, objects with less mass need less force (force = mass x acceleration)
3. for every action there is an equal an opposite reaction
Ms. Sir says that her door squeaks and is hard to open. Mr. Maam looks at the door and tells her she needs to oil the door hinges. Explain why oiling the door hinges would help Ms. Sir.
Oiling the hinges puts a thin layer of fluid between metal parts of that rub against each other. Since fluid friction is less than sliding friction, Ms. Sir will find the door easier to open and quieter.
What is the difference between speed and velocity?
Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object’s movement