A distance-time graph indicates than an object moves 100 m in 4 s and then remains at rest for 6 s. What is the average speed of the object?
A.
50 m/s
B.
25 m/s**
C.
10 m/s
D.
100 m/s
Which example identifies a change in motion that produces acceleration?
A.
a speed skater moving at a constant speed on a straight track
B.
a ball moving at a constant speed around a circular track
C.
a particle moving in a vacuum at a constant velocity
D.
a vehicle moving down the street at a steady speed***
When an unbalanced force acts on an object,
A.
the object’s motion does not change.****
B.
the object accelerates.
C.
the weight of the object decreases.
D.
the inertia of the object increases.
As you push a cereal box across a tabletop, the sliding friction acting on the cereal box
A.
acts in the direction of motion.***
B.
equals the weight of the box.
C.
is usually greater than static friction.
D.
acts in the direction opposite of motion
Projectile motion is caused by
A.
the downward force of gravity.***
B.
the initial forward velocity.
C.
a final vertical velocity.
D.
the downward force of gravity and an initial forward velocity.
Please check my answers
To calculate the average speed of the object, we need to consider the total distance traveled and the total time taken. In this scenario, the object moves 100 m in 4 s and then remains at rest for 6 s.
To find the average speed, we use the formula:
Average Speed = Total Distance / Total Time
For this particular situation:
Total Distance = 100 m
Total Time = 4 s + 6 s = 10 s
Plugging these values into the formula:
Average Speed = 100 m / 10 s = 10 m/s
Hence, the correct answer is C. 10 m/s.
For the second question, which asks for an example that identifies a change in motion that produces acceleration, the correct answer is D. a vehicle moving down the street at a steady speed. Acceleration refers to a change in velocity, which involves either a change in speed or a change in direction. In the given options, a vehicle moving at a steady speed down the street would experience acceleration when it changes its speed or direction.
When an unbalanced force acts on an object, the correct answer is B. the object accelerates. Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Therefore, when an unbalanced force acts on an object, it will cause a change in its motion, resulting in acceleration.
Regarding the sliding friction acting on a cereal box as it is pushed across a tabletop, the correct answer is A. acts in the direction of motion. Sliding friction acts parallel to the surfaces in contact and opposes the relative motion between them. In this case, as the cereal box is being pushed in a particular direction, the sliding friction acts in the same direction to resist the motion.
Regarding projectile motion and its causes, the correct answer is A. the downward force of gravity. Projectile motion is the motion of an object that is launched into the air and is subject only to the force of gravity and its initial velocity. The force of gravity acts downward, causing the object to follow a curved path.