Physics 1-3

19 terms by mtierney

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false

the change in position vector of a moving object is equal to the distance it has moved

false

if a bird is moving at 3.5 m/s at a certain instant of time then it will travel 3.5 m in the next second

true

If the average speed of an object is zero, then its average velocity must be zero; but if its
average velocity is zero, its average speed is not necessarily zero.

false

If a vector pointing to the right has a positive magnitude, then one pointing to the left has a
negative magnitude.

true

Negative acceleration is called deceleration because an object is slowing down.

false

If an object stops moving at a point, then its acceleration must be zero at that point.

false

It is physically impossible for an object to have a negative acceleration and yet be speeding
up.

false

The product of a vector by a scalar is a vector having the same direction of the original vector
but a different magnitude.

true

The magnitude of a vector cannot be smaller than the magnitude of any of its components.

false

The magnitude of the resultant of two vectors must be greater than or equal to the magnitude
of each of these vectors.

false

The magnitude of the displacement vector from A to B can never be less than the distance
from A to B, but it can be greater than that distance.

false

The magnitude of the displacement vector of an object is equal to the distance that object has
moved.

false

A grasshopper leaps into the air at a 62 degree angle above the horizontal. At its highest
point, the grasshopper's velocity and acceleration are equal to zero.

true

You throw a 5.0 kg stone from the top of a cliff with an initial vertical velocity of 8.0 m/s
downward and an initial horizontal velocity of 7.0 m/s away from the cliff, and it feels no air
resistance. After the stone is in the air but free of your hand, its acceleration remains constant
at 9.8 m/s2 downward but its speed changes.

false

You can launch a projectile with a fixed initial speed but at any angle above the horizontal,
and it feels no air resistance. The time for it to return to the ground does not depend on the
angle at which you throw it.

true

A ball is thrown at an angle above the horizontal from the top of a cliff and feels no air
resistance. A runner at the base of the cliff moves horizontally so that she is always under the
ball. In this runner's reference frame, the path of the ball is a straight line rather than a
parabola.

false

A football is kicked toward the goal posts and feels no air resistance. While it is in the air, the
only force acting on it is 9.8 m/s2 downward due to gravity.

true

Projectiles subject to constant acceleration in two dimensions.

true

To achieve maximum range of a projectile, for a fixed initial velocity, on Earth we must
launch it at 45°.

Example: