Multiple Choice, Conceptual
When a projectile reaches the highest point the horizontal component of the acceleration is...
A. Less than g
B. Positive g
C. Negative g
D. Zero
D : Zero, because gravity provides the same acceleration to the ball on the way up (slowing it down) as on the way down (speeding it up), the time to reach maximum altitude is the same as the time to return to its launch position.
A free-falling object is a projectile. T or F
True
A ball is thrown at an angle of 38 degrees to the horizontal. What happens to the magnitude of the ball's vertical acceleration during the total time interval that the ball is in the air.
It remains the same
a=g=9.8 m/s^2 constant
xf = xi + vix(Δt) + (__)(__)(Δt)2
(1/2)(ax)
The path of a projectile is...
trajectory
When a projectile reaches the highest point the vertical component of the acceleration is
A. Greater than g
B. Positive g
C. Negative g
D. Zero
C : Negative g, though the acceleration due to gravity always acts downwards, it is in a direction opposite to the motion of the projectile when the projectile is moving upwards, which means that it becomes ‘−g’ with respect to the projectile trajectory.
The speed of the falling object is proportional to its weight or mass. T or F
The acceleration of the all falling objects is same, so speed is also constant
Is the vertical velocity at the top of projectile motion greater than the velocity at any other point?
No, it is zero at the top of projectile motion because at this point the ball has come to rest.
Velocity : vy = vi (______) - gt
vy = vi (sin θ) - gt
A quantity that has both magnitude and direction...
vector
Trajectory
A. The path an object in free fall takes
B. An object in free fall
C. Horizontal displacement of the object's path
D. Vertical displacement of the object's path
A. The path an object in free fall takes
The magnitude of the vertical velocity of a projectile changes by 9.8 m/s each second. T or F
There is a vertical acceleration caused by gravity; its value is 9.8 m/s/s, down, The vertical velocity of a projectile changes by 9.8 m/s each second
One car travels due east at 40 km/h, and a second car travels north at 40 km/h. Are their velocities equal?
No, because the magnitude of the two velocities is equal but the directions are not.
vf2y = vi2 + ______
v2y = u2y + 2ays
Occurs when air resistance is negligible and the only force acting on an object is gravity...
free fall
A 0.2 kg red ball is thrown horizontally at a speed of 4 m/s from a height of 3 m. A 0.4 kg green ball is thrown horizontally from the same height at a speed of 8 m/s. Compared to the time it takes the red ball to reach the ground, the time it takes the green ball to reach the ground is
A. Half as much
B. One quarter as much
C. The same
D. Twice as much
E. Four times as much
C, because If both balls are thrown from the same height horizontally, they will both strike the ground at the same time (because all of the vertical variables are the same).
An object which is moving through the air and not touching any surface is always a projectile. T or F
False, because object moving through air have air resistance
A ball is thrown horizontally at a speed of 24 meters per second from the top of a cliff. If the ball hits the ground 4.0 seconds later, approximately how high is the cliff
Vyi = 0 m/s, t =4s
dy = 1/2 gt^2
=1/2 (9.8)(4)^2
=78 m
The product of the force and the lever arm that may cause rotational motion is...
Torque
If the acceleration of an object is always directed perpendicular to its velocity,
A. the object is speeding up.
B. the object is slowing down.
C. the object is turning.
D. this situation would not be physically possible.
C) the object is turning.
Acceleration that is perpendicular to velocity changes ONLY the velocity's direction.
Any object upon which air resistance is negligible is a projectile. T or F
False, for a projectile, after the initial force that launches the object, air resistance is negligible and the only other force that object experiences is the force of gravity.
One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level?
Neither because they both have the same speed at the impact. They undergo the same acceleration because of the gravity during free fall and projectile motion, so the speed is equal.
A force which keeps a body moving with a uniform speed along a circular path and is directed along the radius towards the center...
Centripetal force