Physics Semester Exam 1

When something falls to the ground, it accelerates due to the force of gravity pulling it downwards. This acceleration is called the acceleration due to gravity. On Earth's surface, the value of this acceleration is approximately 10 m/s2.

The net force on an object is the vector sum of all the forces acting on it. In this case, the 15-N force and the 45-N force act in opposite directions. Since they have the same magnitude, the net force is equal to the difference between the two forces, which is 45 N - 15 N = 30 N.

The car starts from rest and reaches a velocity of 42 m/s in 7 seconds. Average acceleration is calculated by dividing the change in velocity by the time taken. In this case, the change in velocity is 42 m/s (final velocity) - 0 m/s (initial velocity) = 42 m/s. The time taken is 7 seconds. Therefore, the average acceleration is 42 m/s / 7 s = 6 m/s2.

The car's acceleration can be calculated by finding the change in velocity divided by the time taken. In this case, the change in velocity is 5 km/h and the time taken is 1 second. Therefore, the acceleration is 5 km/h•s.

When a ball is thrown straight up, it reaches its highest point at the top of its path. At this point, the ball momentarily comes to a stop before it starts to fall back down. This means that its velocity is zero at the top of its path. Instantaneous speed is the magnitude of the velocity vector, so the instantaneous speed at the top of the path is also zero.

The correct answer is "all of the above" because each option listed - miles per hour, light years per century, and kilometers per hour - can be used as a unit of speed. Speed can be measured in different units depending on the context and the system of measurement being used. Therefore, all three options are valid units of speed.

When an object is freely falling, it experiences acceleration due to gravity. The acceleration due to gravity is approximately 9.8 m/s^2. Since the object starts from rest, its initial velocity is 0 m/s. 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 after 6 seconds. Plugging in the values, we get v = 0 + (9.8)(6) = 58.8 m/s. Rounding off, the speed of the object after 6 seconds of falling will be about 60 m/s.

In free fall, the object falls with an increasing velocity due to the acceleration of gravity. As time progresses, the object gains speed and covers a larger distance in each subsequent second compared to the previous second. Therefore, the correct answer is that the object falls a larger distance than in the second before.

A freely falling object accelerates due to the force of gravity. The acceleration is approximately 9.8 m/s^2. This means that the object's speed increases by 9.8 m/s every second. Therefore, if the object were equipped with a speedometer, its speed reading would increase by about 10 m/s each second.

The pencil is not moving relative to the desk because it is at rest on the desk. Therefore, its speed relative to the desk is 0 km/s. However, the pencil is on the Earth, which is moving around the sun at a speed of 30 km/s. Therefore, the pencil is also moving at the same speed as the Earth relative to the sun, which is 30 km/s.

The correct answer is "is g; no more, no less." This means that the jumper's acceleration is equal to the acceleration due to gravity, which is approximately 9.8 m/s^2. Regardless of the player's body orientation, launch speed, or height, their acceleration will always be the same while they are in the air.

Equilibrium occurs when all the forces acting on an object are balanced, meaning that the sum of the +x forces on an object equals the sum of the –x forces, the net force on the object is zero, and the sum of the upward forces equals the sum of the downward forces. In other words, all of these conditions must be met simultaneously for an object to be in equilibrium.

Acceleration is defined as the rate at which an object's velocity changes over time. It is calculated by dividing the change in velocity by the time interval. This means that acceleration is equal to the amount by which an object's velocity increases or decreases per unit of time. Therefore, the correct answer is "velocity divided by the time interval."

In the absence of air resistance, objects fall at a constant acceleration. This means that the speed at which the object falls increases by the same amount every second. The object's velocity (speed and direction) will also increase, but at a constant rate. The distance the object falls will also increase each successive second, but this is a result of the acceleration. Therefore, the correct answer is acceleration.

When drops of water fall from a water faucet, they are subject to gravity. As they fall, the force of gravity causes them to accelerate, resulting in an increase in their distance from each other over time. Therefore, the drops of water get farther apart as they fall.

The weight of a person is always directed straight down, regardless of their position or the slope of the ground. This is because weight is a force that is caused by gravity and acts towards the center of the Earth. Therefore, even if a person is standing on a hill, their weight will still be directed straight down towards the Earth's center.