Physics Forces Quiz 08

In an emergency stop, a 1500-kg vehicle loses 300,000 joules of energy as it comes to rest. What was the speed of the vehicle the moment the brakes were applied?

• 10 m/s

• 14 m/s

• 20 m/s

• 25 m/s

Answer explanation

Using the kinetic energy formula KE = 0.5 * m * v^2, we can rearrange it to find v. Given KE = 300,000 J and m = 1500 kg, we solve for v: v = sqrt(2 * KE / m) = sqrt(2 * 300,000 / 1500) = 20 m/s.

Tags

NGSS.HS-PS3-1

If the kinetic energy of an object is 16 J when its speed is 4 m/s, what is the object’s mass?

• 0.5 kg

• 2.0 kg

• 8.0 kg

• 19.6 kg

Answer explanation

Kinetic energy (KE) is given by the formula KE = 0.5 * m * v^2. Rearranging for mass (m), we have m = 2 * KE / v^2. Substituting KE = 16 J and v = 4 m/s, we find m = 2 kg, which is the correct answer.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-2

If a 5-kg mass is raised two meters vertically from the surface of Earth, its gain in gravitational energy will be:

• 5 J.

• 10 J.

• 20 J.

• 100 J.

Answer explanation

The gain in gravitational energy is calculated using the formula: Energy = mass × gravity × height. Here, Energy = 5 kg × 10 m/s² × 2 m = 100 J. Thus, the correct answer is 100 J.

Tags

NGSS.MS-PS3-2

A spring has a spring constant of 120 N/m. How much energy is stored in the spring as it is stretched a distance of 0.20 meter?

• 2.4 J

• 4.8 J

• 12 J

• 24 J

Answer explanation

The energy stored in a spring is given by the formula E = 0.5 * k * x^2. Here, k = 120 N/m and x = 0.20 m. Thus, E = 0.5 * 120 * (0.20)^2 = 2.4 J. Therefore, the correct answer is 2.4 J.

Tags

NGSS.HS-PS3-1

A 0.50-kg ball is thrown vertically upward with an initial velocity of 35 m/s. Approximately, how high will the ball rise?

• 35 m

• 60 m

• 85 m

• 120 m

Answer explanation

To find the maximum height, use the formula h = (v^2) / (2g), where v = 35 m/s and g = 9.81 m/s². This gives h ≈ 60 m, confirming the correct answer is 60 m.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS2-1

NGSS.HS-PS3-2

NGSS.HS-PS2-4

A baseball bat strikes a baseball that is at rest, and as a result the baseball flies away from the bat. The kinetic energy gained by the baseball as it leaves the bat is due to the:

• loss of gravitational energy of the ball as it falls back to the ground.

• gain in gravitational energy as the ball rises to the peak of its trajectory.

• loss of mass after the ball is hit.

• work done by the bat on the ball.

Answer explanation

The kinetic energy gained by the baseball is due to the work done by the bat on the ball. The bat transfers energy to the ball upon impact, causing it to accelerate and fly away.

Tags

NGSS.HS-PS3-1

A catapult with a spring constant of 10,000 N/m is used to launch a target from the deck of a ship. The spring is compressed a distance of 0.5 m before the 1.56-kg target launched. What is the target’s velocity as it leaves the spring?

• 10 m/s

• 20 m/s

• 30 m/s

• 40 m/s

Answer explanation

Using the formula for potential energy in a spring, PE = 0.5 * k * x^2, where k = 10,000 N/m and x = 0.5 m, we find PE = 1250 J. Setting this equal to kinetic energy (KE = 0.5 * m * v^2) and solving for v gives 40 m/s.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS2-1

A ball is thrown vertically upward. As the ball rises, the ball’s total energy:

• decreases

• increases

• remains the same

Answer explanation

The ball's total energy remains the same as it rises because energy is conserved in the absence of air resistance. The kinetic energy decreases while potential energy increases, but the total energy stays constant.

Tags

NGSS.MS-PS3-2

NGSS.MS-PS3-5

NGSS.MS-PS3-1

Potential energy due to an object's compression or extension is called ___________ potential energy.

• elastic

• kinetic

• static

• gravitational

Answer explanation

Potential energy due to an object's compression or extension is known as elastic potential energy. This type of energy is stored when materials are deformed and can be released when they return to their original shape.

An object is lifted upward at a constant speed. The gain in gravitational energy of the object is due to the:

• work done on the object.

• total force applied to the object.

• change in kinetic energy of the object.

• weight of the object.

Answer explanation

The gain in gravitational energy occurs because work is done on the object against gravity. Since the object is lifted at a constant speed, the work done equals the increase in gravitational potential energy.

Tags

NGSS.MS-PS3-2

NGSS.MS-PS3-5