1.
On a position-time graph, a changing velocity is represented by a straight line.
Correct Answer
B. False
Explanation
A changing velocity is not represented by a straight line on a position-time graph. Instead, a changing velocity is represented by a curve on a position-time graph. This is because velocity is the rate of change of position over time, so if the velocity is changing, it means that the rate of change of position is also changing, resulting in a curved line on the graph.
2.
Speed is
Correct Answer
D. All of the above
Explanation
The correct answer is "all of the above" because speed is indeed a measure of how fast something is moving, it is also the distance covered per unit time, and it is always measured in terms of a unit of distance divided by a unit of time. Therefore, all three statements are true and provide a comprehensive explanation of what speed is.
3.
As a ball falls freely, the distance it falls each second is the same.
Correct Answer
A. True
Explanation
The statement is true because when a ball falls freely, it is only under the influence of gravity. In this case, the acceleration due to gravity remains constant, which means that the ball's velocity increases by the same amount every second. As a result, the distance it falls each second is also the same. This is known as uniform acceleration, and it applies to objects falling freely near the surface of the Earth.
4.
If an object moves from one position to another, it is
Correct Answer
B. Moving
Explanation
The correct answer is "moving" because the question states that the object moves from one position to another. This implies that the object is in motion or moving. The other options such as "accelerating," "speeding," and "in free fall" are not necessarily true based on the information given in the question.
5.
Objects in free fall are only influenced by gravity, not by air resistance.
Correct Answer
A. True
Explanation
Objects in free fall are only influenced by gravity, not by air resistance. This is because in free fall, the only force acting on the object is the force of gravity. Air resistance, on the other hand, is a force that opposes the motion of objects through the air. However, in free fall, the object is typically falling through a vacuum or in a situation where the effects of air resistance are negligible. Therefore, in these conditions, the object is only influenced by gravity and not by air resistance.
6.
Elapsed time is the time that passes from the beginning to the end of a fall.
Correct Answer
A. True
Explanation
The statement is true because elapsed time refers to the total amount of time that has passed between the start and end of a particular event or activity, in this case, a fall. It measures the duration from the beginning to the end, capturing the entire time span of the fall. Therefore, the answer is true.
7.
Calculate your average walking speed when you step 1 meter in 0.5 seconds.
Correct Answer
2 m/s
Explanation
The average walking speed can be calculated by dividing the distance traveled by the time taken. In this case, the distance traveled is 1 meter and the time taken is 0.5 seconds. Dividing 1 meter by 0.5 seconds gives us a speed of 2 meters per second.
8.
When you look at the speedometer in a moving car, you can see the car's
Correct Answer
A. Instantaneous speed
Explanation
When you look at the speedometer in a moving car, you can see the car's instantaneous speed. Instantaneous speed refers to the speed of an object at a specific moment in time. The speedometer in a car measures the current speed of the car, providing the driver with real-time information about how fast the car is moving at that particular moment. It does not provide information about the average speed, acceleration, or distance traveled over a period of time.
9.
Calculate the distance (in km) that Charlie runs if he maintains an average speed of 8 km/hr for 1 hr.
Correct Answer
8 km, 8, 8km, 8 kilometers, 8 kms, 8kms
Explanation
Charlie runs for 1 hour at an average speed of 8 km/hr. This means that for every hour, he covers a distance of 8 km. Therefore, the distance that Charlie runs is 8 km.
10.
Calculate the distance you will travel if you maintain an average speed of 10 m/s for 40 seconds.
Correct Answer
400 m, 400m, 400 meters
Explanation
If you maintain an average speed of 10 m/s for 40 seconds, you can calculate the distance traveled by multiplying the speed by the time. In this case, 10 m/s multiplied by 40 seconds equals 400 m.
11.
Acceleration describes
Correct Answer
E. All of the above
Explanation
Acceleration describes any change in velocity. This includes an object that is speeding up, an object that is slowing down, and an object that is changing direction. Acceleration is a vector quantity that measures the rate at which an object's velocity changes over time. It can be positive when the object is speeding up, negative when the object is slowing down, or even zero when the object's velocity remains constant. Therefore, all of the given options are correct explanations of acceleration.
12.
Calculate the speed of a bowling ball that moves 8 meters in 4 seconds.
Correct Answer
2 m/s, 2m/s
Explanation
The speed of an object is calculated by dividing the distance it travels by the time it takes to travel that distance. In this case, the bowling ball moves 8 meters in 4 seconds. Dividing 8 meters by 4 seconds gives us a speed of 2 meters per second.
13.
Calculate the acceleration of a bus that goes from 10 km/h to a speed of 50 km/h in 10 seconds. (Convert it in m/s^2, approximate up to 2 decimal places)
Correct Answer
1.11 m/s^2, 1.11m/s^2
Explanation
To calculate acceleration, use the formula:
Acceleration (a) = Change in Velocity / Time Taken
First, convert speeds from km/h to m/s:
Initial velocity (u) = 10 km/h * (1 / 3.6) m/s ≈ 2.78 m/s
Final velocity (v) = 50 km/h * (1 / 3.6) m/s ≈ 13.89 m/s
Change in velocity (v−u) = 13.89 m/s - 2.78 m/s = 11.11 m/s
Now, plug these values into the formula for acceleration:
a=11.11 m/s/10 s
a≈1.11m/s^2
Therefore, the acceleration of the bus is approximately 1.11 m/s².
14.
Calculate the speed (in m/s) of a skateboarder who accelerates from rest for 3 seconds down a ramp at an acceleration of 5 m/s2.
Correct Answer
15 m/s, 15m/s
Explanation
The skateboarder starts from rest, which means their initial velocity is zero. They accelerate at a rate of 5 m/s^2 for 3 seconds. Using the equation v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time, we can calculate the final velocity. Plugging in the values, we get v = 0 + 5 * 3 = 15 m/s. Therefore, the speed of the skateboarder is 15 m/s.
15.
Suppose you take a trip that covers 240 km and takes 4 hours. Your average speed is
Correct Answer
D. 60 km/h.
Explanation
The average speed is calculated by dividing the total distance traveled by the total time taken. In this case, the total distance is 240 km and the total time is 4 hours. Therefore, the average speed is 240 km divided by 4 hours, which equals 60 km/h.
16.
Calculate the vertical distance an object dropped from rest would cover in 12 seconds if it fell freely without air resistance.(Take g=9.8 m/s^2)
Correct Answer
705.6 m, 705.6m
Explanation
An object in free fall, without air resistance, accelerates at a constant rate of 9.8 m/s^2. The equation to calculate the distance covered by an object in free fall is given by d = 1/2 * g * t^2, where d is the distance, g is the acceleration due to gravity, and t is the time. Substituting the given values, d = 1/2 * 9.8 * 12^2 = 1/2 * 9.8 * 144 = 705.6 m. Therefore, the vertical distance covered by the object in 12 seconds is 705.6 m.
17.
An apple drops from a tree and hits the ground in 1.5 seconds. Calculate how far it falls. (Approximate up to 2 decimal places)
Correct Answer
11.02 m, 11.03 m, 11.02m, 11.03m
Explanation
Distance fallen = 1/2 × acceleration due to gravity × time²
Using standard values:
Distance fallen = 1/2 × 9.8 m/s² × (1.5 s)²
Distance fallen ≈ 1/2 × 9.8 m/s² × 2.25 s²
Distance fallen ≈ 11.027 ≈ 11.02 ≈ 11.03 meters
So, the apple falls approximately 11.03 meters before hitting the ground.
18.
Calculate the acceleration of a ball that starts from rest and rolls down a ramp and gains a speed of 25 m/s in 5 seconds.
Correct Answer
5 m/s^2, 5m/s^2
Explanation
The acceleration of an object is determined by the change in its velocity over time. In this case, the ball starts from rest and gains a speed of 25 m/s in 5 seconds. To calculate the acceleration, we can use the formula
acceleration = change in velocity/time.
The change in velocity is 25 m/s (final velocity) - 0 m/s (initial velocity), which is 25 m/s.
Dividing this by the time of 5 seconds gives us an acceleration of
5 m/s/s = 5 m/s^2
19.
Calculate the instantaneous speed (in m/s) at the 10-second mark for a car that accelerates at 2 m/s2 from a position of rest.
Correct Answer
20 m/s
Explanation
The car starts from rest, which means its initial velocity is zero. It then accelerates at a constant rate of 2 m/s^2. To calculate the instantaneous speed at the 10-second mark, we can use the equation: final velocity = initial velocity + (acceleration * time). Plugging in the values, we get: final velocity = 0 + (2 * 10) = 20 m/s. Therefore, the instantaneous speed at the 10-second mark is 20 m/s.
20.
A position-time graph of constant velocity will show a
Correct Answer
A. Straight line.
Explanation
A position-time graph represents the motion of an object over time. When an object has a constant velocity, it means it is moving at a steady speed in a straight line. Therefore, the position-time graph for constant velocity will also be a straight line. This is because the object covers equal distances in equal intervals of time, resulting in a linear relationship between position and time.