Section 1
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Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?
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Date created
Mar 1, 2020
Cards (93)
Section 1
(50 cards)
Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?
Exactly g
You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward?
There is not a force causing you to slide forward
If the velocity of an object is zero, the object cannot be accelerating. True or False?
False, gravity exists
A football is kicked into the air @ an angle of 45º with the horizontal. At the very top of the ball's path, its velocity is
Entirely horizontal
A bullet is fired horizontally and hits the ground in 0.5s. If it had been fired with twice the speed in the same direction, it would've hit the ground in...
0.5s. (height determines time, speed determines distance)
If you ignore the air resistance of a projectile in motion, the ____________ of the projectile remains constant.
Horizontal component of the velocity vector
A football is kicked into the air @ an angle of 45º with the horizontal. At the very top of the ball's path, its acceleration is
Entirely vertical
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The friction force on the box due to the floor is equal to
Pcosø
If the velocity is zero at one instant, what is true about the acceleration of the object?
-Acceleration could be positive -Acceleration could be negative
An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg. What is the reaction force to this pull?
The object is pulling upward on the earth with force MG
A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled?
160 N
You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is
slowing down
A baseball is thrown with a velocity V and an angle ø with the horizontal. The horizontal component of its velocity is...
Vcosø
Roll a bowling ball of the edge of a table. As it falls, its horizontal component of velocity...
Remains constant
At what point in its path is the vertical component of velocity the smallest?
At the top
Inside of a truck a ball of weight mg is hanging by a light wire at rest from the ceiling. The wire makes an angle ø with the ceiling, as shown in the figure. Which one of the following conditions must be true about the tension T in the wire?
Tcosø=mg
Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is
less than F but not zero
A person is using a rope to lower a 5.0 N bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket?
5.0 N
A bullet shot horizontally from a gun..
Hits the ground at the same time a bullet dropped vertically will hit the ground.
(cont.) If you add one more brick to the number found in 16, which string will break?
Top wire has the most tension
Brick A is dropped from the top of a building. Brick B is thrown straight down from the same building, and neither one experiences appreciable air resistance. Which statement about their accelerations is correct?
The 2 bricks have the exact same acceleration.
A 10-kg rock and a 20-kg rock are dropped from the same height and experience no significant air resistance. If the 20-kg rock reaches the ground with a time T, what time will the 10-kg rock hit the ground?
Exactly T.
The slope of a velocity versus time graph gives...
Acceleration
If the velocity versus time graph of an object is a straight line with a non-zero slope with the time axis, the object is...
Moving with a constant nonzero acceleration
The slope of a position versus time graph gives...
Velocity
A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed Vo and experience no significant air resistance. If the 10-kg rock reachers a maximum height H, what maximum height will the 20-kg rock reach?
Exactly H. Mass does not matter without air resistance.
A bomber flying in level flight with constant velocity drops a bomb before its over the target. Neglecting air resistance, which of the following isn't true?
The horizontal velocity of the plane equals the vertical velocity of the bomb as it is dropped.
A very light wire is used to hang a series of 8.0 kg bricks. This wire will break if the tension in it exceeds 450 N. The bricks are hung one below the other from a hook in the ceiling using this wire, as shown in the figure. *Use 10 m/s2 for acceleration due to gravity. How many whole bricks can be hung without breaking the wire?
5 10x8=80 450/80= 5
The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth?
Mass is the same but weight is less
Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by the object.
The displacement is either less than or equal to the distance traveled
At what point in its path is the horizontal component of velocity the smallest?
It is the same throughout the path
If the velocity of an object is zero at some point, then its acceleration must also be zero at that point. True or False?
False, gravity exists at all times
An object is undergoing free fall motion. As it falls, the object's...
Speed increases
A woman is straining to lift a large crate of bananas, but without success because it is too heavy. We denote the forces on the crate as follows: F is the magnitude of the upward force being exerted on the crate by the person, N is the magnitude of the vertical contact force on the crate by the floor, and mg is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?
F+N=mg
An object is moving with constant non-zero velocity. Which of the following statements about it must be true?
The net force the object is zero
When a ball is thrown upward with no air resistance, the acceleration at the highest point is...
Downward
A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about force of static friction f on the block?
f=mgsinø
A golfer drives her ball from the tee down the fairway in a high arching shot. When the ball is at the height of its flight...
Its velocity and acceleration are both nonzero (its vertical velocity is 0, but its horizonatl component is nonzero.)
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to
W+Psinø
A person who normally weighs 700 N is riding in an elevator that is moving upward but slowing down at a steady rate. If this person is standing on a bathroom scale inside the elevator, what would the scale read?
Less than 700
A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?
120 N
When is the average velocity of an object is equal to instantaneous velocity?
When Velocity is constant
Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? Neglect air resistance.
They're traveling at the same speed
A stone of mass M is dropped from an airplane that has a horizontal velocity V at height H above a lake. If theres no air resistance, the horizontal distance R from the point on the lake directly below the point of release to the point where the stone strikes the water is given by which formula?
R=v√(2h/g)
A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball going up is correct?
Its velocity points upward and its acceleration points downward
When a 45 kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true?
The elevator is accelerating upward at a constant rate and from the given information we cannot tell if it is moving up or down
You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure. The reaction force to your push is
The push of box G against you
A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the rope must be
Equal to the weight of the bucket
An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be
Greater that the weight of the elevator
An airplane moves at 141 km/hr towards the northeast (45º). What is its component of velocity in the northward direction?
141sin(45)=x x=99.7km/hr (aka 100)
Section 2
(43 cards)