Solutions: Speed, Velocity, and Acceleration-1



In Brief

This page includes solutions to the set of questions related to the Speed, Velocity, and Acceleration.
This helps learners to ensure their learning on aspects of physics in general but also Speed, Velocity, and Acceleration questions mentioned in the quiz section.

Questions: With Solutions on Speed, Velocity, and Acceleration:

Question 1:

A quantity used to measure how the velocity changes over time is called
Answer: acceleration.

Question 2:

A school child throws a ball downward from rest and then realized that the ball covers a distance of 1.0 m in a time of 5.0 s.
Calcualte the ball's acceleration.
Answer: 0.8 m/s2
Explanation:
Average velocity = 1 m / 5 s = 0.20 m/s, average velocity during 5 s.
The initial velocity was zero and the final velocity is more than 0.20 m/s.
Since average velocity = (initial velocity + final velocity)/ 2 = 0.20 m/s,
this implies that final velocity = 2 × average velocity − 2 × initial velocity = 0.40 m/s.
Acceleration = change in velocity / total time = (0.4 m/s - 0) / 5 s = 0.8 m/s2


Question 3:

A motorbike runs 50 meters in the first two seconds from point A to point B, then runs 60 more meters from B to C in the next two seconds, and finally, runs for 70 meters from C to D in the last two seconds. Calculate the acceleration of the motorbike.
Answer: 2.5 m/s2
Explanation:
Let's note distance by d, time by t, speed by v and acceleration by a
d = vi × t + ½ × a × t2
So, from A to B, equation (1): 50 m = vi × 2 + ½ × a × 22
From A to C, d = 50 m + 60 m = 110 m and t = 2 s + 2 s = 4 s; hence equation (2); 110 m = vi × 4 + ½ × a × 42
From equation 1), vi = 25 − a; replacing this in equation 2); vi4 + ½a16 = 110 is equivalent to 100 − 4a + 8a = 110
We obtain a = 2.5 m/s2 and vi = 25 - 2.5 = 22.5 m/s.
Let's double check these findings in equation 3 which is from A to D where d = 50 + 60 + 70 = 180 m and t = 2 s + 2 s + 2 s = 6 s
d = vi × 6 + ½ × a × 62 = 22.5 m/s × 6 s + ½ × 2.5 m/s2 × 36 s = 135 m + 45 m = 180 m
This is exactly what distance is between A and D.

Question 4:

A motorbike starts from rest, and then goes through a contant acceleration and travels a distance of 1000 meters.
The motorbike reaches a final speed of 100 meters/second.
Calcualte the time it takes the motorbike to cover 1000 meters.
Answer: 10 s

Explanation:
time = speed / distance = 1000 / 100 = 10 s

Question 5:

Select one of the correct answers when a boat travels at constant speed.
Answer: can change direction.

Question 6:

A school child throws a ball downward from rest and then realized that the ball covers a distance of 2.0 m in a time of 4.0 s.
Calculate the ball's average speed.
Answer: 0.5 m/s.
Explanation:
average speed = total distance / total time = 2 m / 4 s = 0.5 m/ s

Question 7:

Which two quantities will always have the same magnitude?
Answer: instantaneous speed and instantaneous velocity.

Question 8:

Which of the following quantities relating to motion is not a vector?
Answer: speed.

Question 9:

A car starts from rest and reaches 40 m/s in 10 seconds.
The average acceleration of the car is
Answer: 4 m/s2

Explanation:
average speed = change in velocity divided by elapsed time = (40 m/s − 0 m/s) / (10 s − 0 s) = 4 m/s2



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