mc qs Flashcards
under what condition is the average velocity equal to the instantaneous velocity?
when an object is moving with constant velocity
for a car moving fwd and then right, how does the avg speed compare to the avg velocity?
the avg velocity is larger bc the magnitude of the displacement is greater than the distance
a bat hit the ball in the air, the time the ball takes before it hits the ground depends on the…
the angle and the initial speed with which the ball is hit
true or false:
the instantaneous velocity at a particular time is the slope of the displacement-time curve at that position
False
true or false:
an object can be in free fall after it is dropped or after it is thrown upwards
true
true or false:
the addition of 2 displacement vectors depends on the order in which they’re added
false
true or false:
if the velocity vector of an object changes only in direction, the avg acceleration is zero
false
true or false:
for a ball thrown in a parabolic path, the y-comp of velocity is at the highest point in its trajectory is = to 0
true
true or false:
the velocity of 2 cyclists relative to each other, if they’re moving in the same direction with equal speed of 20 m/s is 0
true
the speed of an object moving in a straight line increases from 10 m/s to 20 m/s in 2s. What is the avg acceleration?
5 m/s^2 in the direction of motion of the object
the motion of a projectile… at a particular instant, the magnitude of the hor. comp. of velocity is 5 m/s and the magnitude of the vertical comp is 8m/s. What do you know about the object?
the projectile is ascending
a river flows 8m/s(N) relative to the bank. A boat travels 6m/s(E) relative to the river. What is the magnitude of the velocity of the boat relative to the bank?
10 m/s
true or false:
speed is always a positive quantity or zero, but never negative
true
true or false:
when a moving object starts to slow down on a straight track, the avg acceleration of the object at any time interval after it starts slowing down is positive
false
true or false:
when 2 displacement vectors of equal magnitude are aligned opposite to each other, the resultant displacement is zero
true
true or false:
a ball thrown hor. from a cliff is an example of projectile motion
true
can two displacement vectors of the same length have a vector sum of zero?
yes
a skier jumps off a ramp, in this case, air resistance is not negligible. How will air resistance affect the range and the speed with which she lands on the ground?
both decrease
a pitcher throws a ball, after the ball has left his hand and is moving through the air, which forces are acting on the ball?
a force exerted by air and the downward force of gravity
a person with a mass of 62kg is in an elevator moving at a constant velocity of 2.3 m/s(up). What is the magnitude of the net force acting on the person?
0N
when the net force acting on an object is doubled, the effect on the acceleration of the object will be…
doubled
An object is suspended from a spring balance in an elevator. The reading is 240 N when the elevator is at rest. The spring balance reading changes to 220 N. Which of the following describes how the elevator is moving?
downward with increasing speed
a child with mass m is sliding down a slide that is inclined at an angle above the hor. The magnitude of the normal force on the child is…
mg cos theta
when the normal force is doubled, the coefficient of friction is…
unchanged
true or false:
a golf ball on the moon has the same inertia as it has on Earth
true
true or false:
according to the 3rd law, the forces of action and rxn always act on the same body and balance each other
false
inertia of an object is directly proportional to its…
mass
when a constant net force acts on an object, which quantity remains constant?
acceleration
action and rxn forces…
act on 2 different objects
The tension in a cable supporting a beam at a construction site is less than the weight of the beam. The beam may be…
going up or down with non-uniform velocity
a bike brakes suddenly, and the wheels skid across the ground, the force of friction b/w the wheels and the ground acts…
bwd on both wheels
true or false:
if only 3 forces of equal magnitude act on an object, the object must have a non-zero net force.
false
true or false:
when you pull up on an object at rest on a hor. surface, you decrease the normal force on the object but not the weight of the object
true
how does the acceleration of a non-inertial frame of reference cause objects in the frame to move?
as if a force were acting on them
a car moves around a banked curve at a constant speed over black ice with no friction, what causes the car to accelerate?
hor. component of the normal force
when will a bathroom scale with nothing on it read zero?
in space
true or false:
for two objects moving in the same circular path with different speeds, the faster object experiences less centripetal acceleration
false
true or false:
when 2 objects move in the same circular path with the same speed, the heavier object requires a greater centripetal force
true
true or false:
earth’s surface is an example of a rotating non-inertial frame of reference
true
inertial frame of reference
newtons 1st law holds true
true or false:
an amusement park ride moving down with a constant velocity is an example of a non-inertial frame of reference
false
true or false:
an observer looking down on a passenger in a car driving around a sharp curve would see that the passenger is being pushed by the car in the direction of the curve
true
true or false:
the moon is not an example of an object in uniform circular motion
false
true or false:
a rollercoaster car in free fall has no apparent weight
true
two cars with the same mass are driving around a curved road at different velocities, which car will experience a greater centripetal force, the one moving with the faster velocity or the moving with the slower velocity?
faster
