Force
An object of mass 5 kg rests on a friction-less inclined plane at an angle of 30°.
Which forces should be shown in its free body diagram?
Normal and Gravity.
When the net force acting on an object is zero, what will its acceleration be?
exactly zero.
As a ball falls freely (without friction) toward the ground, its total mechanical energy does what?
Remains the same.
If an object has momentum, then it must also have what?
Kinetic energy.
As a projectile falls, what happens to the components of velocity?
The vertical velocity will increase in magnitude while the horziontal remains the same.
If an object is sliding down an inclined plane with friction.
Which direction does the friction force point in the free body diagram?
Backwards.
A swimmer pushes backward against the water with her hands. According to Newton’s 3rd Law.
what happens as a result?
The swimmer moves because the water pushes back with an equal force.
As an object freely falls from a building, what happens to the energy of the object as it falls?
Its potential energy decreases and its kinetic energy increases.
In the event of an automobile accident, the safety of the occupant is dependent on the time during collision being extended because?
Greater time means less force.
Which of the following variables would you need in order to calculate how long it would take a horizontally launched projectile to hit the ground?
Only the height of the object.
13)Newton’s Universal Law of Gravitation states that the gravitational force between two objects depend on what.
Mass and Gravity.
Which statement best describes Newton’s 3rd Law of Motion?
Forces always act in pairs that are equal and opposite.
A student throws a stone upward at an angle of 45 degrees. What best describes the stone at the highest point that it reaches?
Its kinetic energy is at a minimum.
Cars crumple to keep you safe in an accident. They do this by what?
A ball is tossed at an angle. It moves in a parabolic path, reaches its highest point, and then falls back to the ground. During the ball’s flight, which of the following statements is true about the direction of the acceleration?
A. It is pointing upward.
B. It is pointing downward.
C. It points opposite its velocity.
D. It points in the same direction as its velocity.
B) It is pointing downward.
A 2 kg book is resting on a table.
What is the normal force exerted by the table on the book?
19.6N.
When a person jumps off a small boat, the boat moves backward. Which law explains this?
Newton's 3rd law.
Which action would require no work to be done on an object?
a) holding the object stationary above the ground
b) pushing the object along a horizontal floor against a frictional force
c) lifting the object from the floor to the ceiling
d) decreasing the speed of the object until it comes to rest
A) holding the object stationary above the ground.
A cannon recoils (kicks back) from launching a cannonball. The velocity of the cannon's recoil is small because the _______________.
The cannon has more mass than the cannonball.
Which of the following scenarios is possible for the resultant velocity of an airplane in a strong wind to be 150 m/s?
A. The wind is blowing at 10 m/s. The airplane is flying against the wind at 140 m/s.
B. The wind is blowing at 20 m/s. The airplane is flying with the wind at 130 m/s.
C. The wind is blowing at 50 m/s. The airplane is flying against the wind at 100 m/s.
D. The wind is blowing at 200 m/s. The airplane is flying with the wind at 50 m/s.
B) The wind is blowing at 20 m/s. The airplane is flying with the wind at 130 m/s.
A car of mass 1000 kg moves around a circular track of radius 50 m at a constant speed of 20 m/s.
What is the magnitude of the car’s centripetal acceleration?
8 M/S^2.
During a baseball game, a bat strikes a ball with a force of 500 N. The ball exerts an equal and opposite force on the bat. If the batter swings with a lighter bat instead of a heavier one.
how will the interaction change?
. A student swings a bat horizontally and makes contact with a ball. The ball leaves the bat, and the bat continues moving through the rest of the swing. Which of the following statements BEST describes the change in energy necessary to do work on the ball?
A. All the kinetic energy of the bat is converted to do work.
B. All the potential energy of the bat is converted to work.
C. Some of the Kinetic energy is converted to work
D. Some of the potential energy of the bat is converted to work.
C) some of the kinetic energy is converted into work.
A 0.005kg firework explodes out of a 0.08kg glass bottle. The bottle kicks backward at 7.5m/s. What is the velocity of the firework going upward?
0.038 m/s
7.5 m/s
1500 m/s
120 m/s
120 M/S
A cannonball is launched horizontally with an initial velocity of 50 m/s off a 100 m tall cliff. The goal is to have the cannonball travel a target range of 400 m. Based on the information provided, will the cannonball reach the target distance?
No, it will fall short of the goal.