Q: A 1600-kg car accelerates from $$15.0\ \mathrm{m/s} to$$ $$40.0\ \mathrm{m/s}. $$What is the minimum energy needed to achieve this change in speed?

$$6.25 \times 10^5$\ \mathrm{J}$$

Question 1

A 1600-kg car accelerates from $$15.0\ \mathrm{m/s} to$$ $$40.0\ \mathrm{m/s}. $$What is the minimum energy needed to achieve this change in speed?

Accepted Answer

$$6.25 	imes 10^5$\ \mathrm{J}$$

Question 2

A box of mass $$6.0\ \mathrm{kg} is $$pushed $$4.0\ \mathrm{m}$$ across a rough warehouse floor by an applied force of $$214\ \mathrm{N} at an $$angle of $$30.0^\circ$$ below the horizontal. The kinetic friction force is $$90.0\ \mathrm{N}. $$What is the work done by the applied force?

Accepted Answer

$$740\ \mathrm{J}$$

Question 3

A $$0.5\ \mathrm{kg}$$ ball is initially at rest on the grass. When the ball is struck by a mallet, the average force exerted on it is $$150\ \mathrm{N}. If $$the ball's speed after being struck is $$1\ \mathrm{m/s}$$, how long was the mallet in contact with the ball?

Accepted Answer

$$0.0033\ \mathrm{s}$$

Question 4

A $$2.0\ \mathrm{kg}$$ object traveling east at $$20.0\ \mathrm{m/s}$$ collides with a $$1.0\ \mathrm{kg}$$ object traveling west at $$10.0\ \mathrm{m/s}. $$After the collision, the $$2.0\ \mathrm{kg}$$ object has a velocity $$5.0\ \mathrm{m/s} to $$the west. How much kinetic energy was lost during the collision?

Accepted Answer

$$250\ \mathrm{J}$$

Question 5

A $$1.5\ \mathrm{kg}$$ car moving at $$25\ \mathrm{m/s}$$ hits an initially uncompressed horizontal ideal spring with spring constant $$2.0 	imes 10^4$\ \mathrm{N/m}. $$What is the maximum distance the spring compresses?

Accepted Answer

$$0.33\ \mathrm{m}$$

Question 6

A $$2.0\ \mathrm{kg}$$ bead slides along a frictionless wire. At point A, the bead is moving to the right with a speed of $$2.0\ \mathrm{m/s}. $$What is the kinetic energy of the bead at point A?

Accepted Answer

$$4.0\ \mathrm{J}$$

Question 7

A shot having a certain initial speed on a horizontal surface comes to rest after traveling $$19.0\ \mathrm{m}. If $$the coefficient of kinetic friction between the object and the surface is $$0.30$$, what was the initial speed of the object?

Accepted Answer

$$10.6\ \mathrm{m/s}$$

Question 8

A $$0.5\ \mathrm{kg}$$ soccer ball is kicked with a force of $$1100\ \mathrm{N}$$ for $$3.0 	imes 10$$^{-3}$$\ \mathrm{s}. $$What is the magnitude of the impulse delivered to the ball?

Accepted Answer

$$3.3\ \mathrm{N \cdot s}$$

Question 9

A $$900\ \mathrm{N}$$ load of bricks is lifted with constant speed to a height of $$10\ \mathrm{m} in$$ $$22.2\ \mathrm{s}. $$What is the minimum power the motor must produce?

Accepted Answer

$$405\ \mathrm{W}$$

Question 10

A $$2.0\ \mathrm{kg}$$ bead slides along a frictionless wire. At point A, the bead is moving to the right with a speed of $$2.0\ \mathrm{m/s}. $$What is the total mechanical energy of the bead?

Accepted Answer

$$4.0\ \mathrm{J}$$

Question 11

A pendulum bob swings from point A to point B along a circular arc. Which of the following best describes the energy transformation?

Accepted Answer

Potential energy transforms into kinetic energy

Question 12

A car skids to a stop along a level highway. In this example, the work being done on the car is:

Accepted Answer

Negative

Question 13

Which of the following situations is an example of an object with a non-zero kinetic energy?

Accepted Answer

A runner moving at the bottom of a cliff

Question 14

A projectile is launched upward with some initial speed. As the projectile goes upward, what energy changes take place?

Accepted Answer

Both kinetic and potential energy decrease

Question 15

Two objects with different masses collide and stick to each other. Compared to before the collision, after the collision:

Accepted Answer

The total momentum of the system is the same

Question 16

In an ELASTIC collision between two objects:

Accepted Answer

Both momentum and the kinetic energy of the system are conserved

Question 17

After a perfectly inelastic collision between two identical carts (one at rest, one moving), what is true about their final motion?

Accepted Answer

Both carts move together with a speed less than the original speed of the moving cart

Question 18

A $$0.5\ \mathrm{kg}$$ ball is initially at rest. If a force of $$150\ \mathrm{N} is $$applied for $$0.0033\ \mathrm{s}$$, what is the final speed of the ball?

Accepted Answer

$$1.0\ \mathrm{m/s}$$

Question 19

A $$1.0\ \mathrm{kg}$$ cart moving at $$0.8\ \mathrm{m/s}$$ collides with an identical cart at rest. After the collision, the carts stick together. What is the final kinetic energy of the system?

Accepted Answer

$$0.16\ \mathrm{J}$$

Work, Energy, and Momentum: Review Sheet and Practice Problems

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