Physics Work Energy Power

A man stands in an elevator as it begins to ascend. Does the normal force from the floor do work on the man?

• Yes, and the work done will be positive.

• Yes, and the work done will be negative.

• Yes, but the sign can’t be determined.

• No.

Tags

NGSS.HS-PS2-1

A 1-kg object is released from rest at the top of a rough-surfaced incline. The object slides without rotating to the bottom of the incline. The object’s kinetic energy at the bottom must be...

• equal to the block’s gravitational potential energy when it was released, because total mechanical energy must be conserved.

• equal to the block’s gravitational potential energy when it was released, because the gain in kinetic energy compensates for the mechanical energy lost to thermal energy on the rough incline.

• less than the block’s gravitational potential energy when it was released, because the gravitational potential energy was converted both to thermal energy and to kinetic energy.

• less than the block’s gravitational potential energy when it was released, because the work done by the friction force must be greater than the block’s gain in kinetic energy.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

A 10-kg wagon moves horizontally at an initial speed of 5 m/s. A 30-N force is applied to the wagon by pulling the rigid handle, which is angled 60° above the horizontal. The wagon continues to move horizontally for another 20 m. A negligible amount of work is converted into thermal energy. By how much has the wagon’s kinetic energy increased over the 20 m?

• 300 J

• 600 J

• 125 J

• 63 J

Tags

NGSS.HS-PS2-1

NGSS.HS-PS3-1

A system consists of two objects having masses m_l and m₂ (m_l < m₂). The objects are connected by a massless string, hung over a pulley as shown, and then released. When the object of mass m₂ has descended a distance h, the potential energy of the system has decreased by...

• (m₂ - m_l)gh

• m₂gh

• (m₁ + m₂)gh

• none of these

Tags

NGSS.HS-PS2-1

NGSS.HS-PS3-1

The following graphs, all drawn to the same scale, represent the net force F as a function of displacement x for an object that moves along a straight line. Which graph represents the force that will cause the greatest change in the kinetic energy of the object from x = 0 to x = x₁?

• 
• 
• 
• 

Tags

NGSS.HS-PS2-1

NGSS.HS-PS3-1

NGSS.HS-PS3-2

A block on a horizontal frictionless plane is attached to a spring, as shown. The block oscillates along the x-axis with amplitude A. Which of the following statements about energy is correct?

• The kinetic energy of the block is at a minimum at x =0.

• The potential energy of the spring is at a minimum at x = A.

• The potential energy of the spring is at a minimum at x = 0.

• The kinetic energy of the block is at a maximum at x = A.

Tags

NGSS.HS-PS3-2

In which of the following situations do your arms do work on books?

• holding a heavy stack of books while standing

• pushing down on a heavy stack of books lying on a table

• dropping a stack of books onto a table

• picking up a pile of books from the floor

Which are correct units for work?

• N x s

• N x m

• J/s

• W

Which are correct equivalent units for power?

• N x s

• N x m

• J

• J/s

Which principle states that whenever work is done, energy changes form?

• Law of Conservation of Energy

• Work-Energy Theorem

• Newton's Fourth Law

• Efficiency