Question 1

A 2 kg object slides without friction on the inside of a vertical circular track of radius $$R = 1\ \mathrm{m}$$ with a constant speed $$v = 4\ \mathrm{m/s}. $$What is the normal force $$N_b$$ acting on the object at the bottom of the trajectory? (Take $$g = 10\ \mathrm{m/s^2$})$$

Accepted Answer

$$N_b = 48\ \mathrm{N}$$

Question 2

A 2 kg object slides without friction on the inside of a vertical circular track of radius $$R = 1\ \mathrm{m}$$ with a constant speed $$v = 4\ \mathrm{m/s}. $$What is the normal force $$N_t$$ acting on the object at the top of the trajectory? (Take $$g = 10\ \mathrm{m/s^2$})$$

Accepted Answer

$$N_t = 8\ \mathrm{N}$$

Question 3

A worker pushes a sled with a force of $$38.0\ \mathrm{N}$$ over a level distance of $$3.60\ \mathrm{m}. If a $$frictional force of $$16.0\ \mathrm{N}$$ acts on the sled in a direction opposite to that of the worker, what net work is done on the sled?

Accepted Answer

$$57.6\ \mathrm{J}$$

Question 4

In a problem using energy considerations to solve for the speed of a ball thrown from the top of a building when it strikes the ground below, where should the potential energy have its zero value?

Accepted Answer

It doesn't matter since only differences in potential energy matter in solutions.

Question 5

Two masses $$m_1$$ and $$m_2$$, with $$m_1$$ \u003c $$m_2$$, have momenta with equal magnitudes. How do their kinetic energies compare?

Accepted Answer

$$KE_1$$ \u003e $$KE_2$$

Question 6

Consider a point on a bicycle wheel as the wheel turns about a fixed axis, neither speeding up nor slowing down. Compare the linear and angular velocities of the point.

Accepted Answer

Both are constant.

Question 7

A $$10.0\ \mathrm{kg}$$ box starts at rest and slides $$3.90\ \mathrm{m}$$ down a ramp inclined at an angle of $$10^\circ$$ with the horizontal. If there is no friction, what is the velocity of the crate at the bottom of the ramp? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$3.70\ \mathrm{m/s}$$

Question 8

A $$2900\ \mathrm{kg}$$ truck moving at $$11.0\ \mathrm{m/s}$$ strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at $$7.00\ \mathrm{m/s}. $$What was the mass of the struck car?

Accepted Answer

$$1300\ \mathrm{kg}$$

Question 9

A roller coaster car of mass $$m is at $$the top of a hill of height $$h. If it $$starts from rest and there is no friction, what is its speed at the bottom of the hill?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 10

A ball of mass $$m is $$dropped from a height $$h$$ and bounces back to a height $$h/2. $$What fraction of the initial mechanical energy is lost during the bounce?

Accepted Answer

$$1/2$$

Question 11

A force $$F is $$applied at an angle $$	heta$$ above the horizontal to move a box a distance $$d$$ across a frictionless surface. What is the work done by the force?

Accepted Answer

$$W = Fd\cos	heta$$

Question 12

A $$5\ \mathrm{kg}$$ object moves in a circle of radius $$2\ \mathrm{m} at a $$constant speed of $$3\ \mathrm{m/s}. $$What is the magnitude of the net force acting on the object?

Accepted Answer

$$22.5\ \mathrm{N}$$

Physics I Practice Exam: Work, Energy, Momentum, and Circular Motion

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