Motion and Force
Explain what a contact and noncontact force is. Give an example of each.
contact: a force only applied when one object actually touches another EX: pushing a shopping cart
noncontact: a force applied to an object whether it touches the object or not. EX: gravity, magnetism, electrical forces
What is the difference between acceleration and velocity?
velocity is speed and direction.
acceleration is change in velocity
What is the difference between balanced forces and action-reaction forces?
balanced forces act on the same object. action-reaction forces act on difference objects
A tow truck pulls a 1,100 kg car and accelerates at a rate of 3 m/s^2. What is the force of the tow truck?
3,300 N
What direction is gravity pulling?
toward the center of the Earth
What is a net force? How do you know what direction the objects are moving?
A combination of all forces acting on that object. The arrows tell us which way it is movng, if it is balanced it will move away from the arrow giving more force
Tony left home at 8AM to spend the day at the amusement park. He arrived at the park, which was 150km from his house, at 10AM. Tony explained tha his speed was 38 km/h. But the fastest speed he went was 60 km/h. What the average speed and the instantaneous speed?
average: 38 km/h
instantaneous: 60 km/h
You push on a door and it opens. Explain what happens in terms of action-reaction forces.
action force- you push the door
reaction force- the door applies an equal and opposite force on you
you are stronger than the door, so the forces are not balanced.
Two classes are playing tug-of-war with a rope. One class pulls on the rope with a 75 N force to the left. while the other pulls with a 40N force to the right. Explain the force and direction. Is it a balanced force?
forces are unbalanced, and the rope net force on the rope is 35N to the left
What is the difference between mass and weight?
Mass- the amount of matter in an object, and it does not change regardless of location
Weight-is the force exerted on an object due to gravity. It depends on both the object's mass and the gravitational pull acting on it.
Why is motion relative? Explain what a reference point is
because motion depends on your reference point. a reference point is what you reference to see something move
What 3 changes in motion show that an object is accelerating?
speeds up, slows down, or changes direction
Label each sentence below that demonstrates the 3 laws of motion. Explain why.
When the mallet hit the ball wiht an action force,, the ball exerts a reaction force on the mallet. The ball starts to move when the mallet applies a net force to it. Once a ball is hit and no longer touches the mallet, it continues moving because of its inertia.
third: When the mallet hit the ball wiht an action force, the ball exerts a reaction force on the mallet.
Second: The ball starts to move when the mallet applies a net force to it.
First: Once a ball is hit and no longer touches the mallet, it continues moving because of its inertia.
Find the net force of a boxy being pushed 6N by Ms. Saunders and 5N by Mrs. Coleman to the right. Mr. Arsenault is pushing 10N to the left. Which way is the box moving and what is the net force?
1N to the right
Describe how each of newtons laws may be observable during a car trip.
1- a rider in the car may shift forward in his seat because of the riders inertia if the car stops suddenly
2- the force exerted by the engine can be found if you know the cars mass and acceleration
3-the car applies a force to the ground, and the ground exerts an equal but opposite force on the car
What is true about the force between a magnet and a steel can?
its s non contact force and a pull
A student graphed distance vs time for an object that moves 14 m every 2m. What is the slope of the line on the graph?
7 m/s. the slope of the line equals the speed on this type of graph
A 12 n net force acts on a 4kg jug of water. What is the resulting acceleration of the jug? Show your calculations.
12N = 4kg X A
a = 12N/4kg =
3m/s^2
A space shuttle travels around the Earth at a constant speed of 28,000 kph. If it takes 90 minutes to complete one orbit, how far is its journey around earth?
42,000 kilometers
How does Newtons first and second law explain why the dishes do not fall off the table when a tablecloth is pulled quickly from underneath them.
because of inertia, which is based on mass. if heavier dishes were used they would have more inertia, so they would be more difficult to accelerate, as explained by Newtons 2nd law. only a net force acting directly on an object can accelerate an object. When pulled, the tablecloth did not have enough time to exert enough force on the dishes to accelerate them.
One man pushed on the front of a cart while another man pushed on the back of the cart. the cart begins to move forward. what are three things you know about these two applied forces?
-they are unbalanced
-the net force is not 0
-strength of the force on the back of the cart is greater than the force on the front
If the line on a distances vs time graph and the line on a speed vs time graph are both straight lines, can the two graphs be displaying the motion of the same object? Explain your answer.
no, a straight line on a distance vs time graph shows an object moving at a constant speed.
a straight line on a speed vs time graph shows an object changing speed
For each of Newton's Laws of motion, compared hitting a 500g croquet ball with a mallet to hitting a 56g tennis ball with the same mallet and the same amount of force.
according to newtons first law, neither ball will move until it is accelerated by a net force. newtons second law states F= MA. According to this law, when the same net force is applied to the 56g ball and the 500g ball, the ball with the smaller mass will experience greater acceleration. for newtons 3rd law, because the net force applied to each ball is the same, the reaction forces that the balls apply to the mallet will be equal
If a car went 56 miles in 60 minutes. Use the information below to find the acceleration from 40-60 minutes.
Distance (miles) Time (min)
0 0
5 10
12 20
20 30
30 40
42 50
56 60
final speed- initial speed
-------------------------------------
Time
.93- .75 / 20(min)
= .009 m/min
Why do objects fall at the same rate regardless of their mass? What affects them falling at different speeds?
air resistance