Question 1

A 720,000 kg locomotive traveling at 120 km/h sees a log on the railroad tracks ahead. The engineer immediately applies the brakes and the locomotive decelerates at $$2.65\ \mathrm{m/s^2$}. $$How far does the locomotive travel before coming to a complete stop?

Accepted Answer

$$209\ \mathrm{m}$$

Question 2

Given the same scenario as above, what is the coefficient of kinetic friction $$\mu_k$$ between the wheels and the track, assuming all the braking force is due to friction?

Accepted Answer

$$0.270$$

Question 3

An arrow is shot horizontally from a bow from a height of $$1.5\ \mathrm{m}$$ with a speed of $$12\ \mathrm{m/s}. $$How much time does it take for the arrow to hit the ground?

Accepted Answer

$$0.55\ \mathrm{s}$$

Question 4

For the same arrow, what is the vertical component of the arrow's speed as it hits the ground?

Accepted Answer

$$-5.4\ \mathrm{m/s}$$

Question 5

A child pulls a $$23\ \mathrm{kg}$$ sled at an angle of $$32^\circ$$ above the horizontal on a flat, grass-covered surface. The coefficient of kinetic friction between the sled and grass is $$0.35. If $$the sled moves at a steady speed of $$2.0\ \mathrm{m/s}$$, what is the magnitude of the normal force between the ground and the sled?

Accepted Answer

$$183\ \mathrm{N}$$

Question 6

A $$200\ \mathrm{g}$$ hockey puck initially at rest starts to slide down a metal ramp that is inclined at a $$40^\circ$$ angle. The coefficient of kinetic friction between the puck and the ramp is $$0.30. $$The incline is $$1.8\ \mathrm{m}$$ long. What is the puck's final speed at the bottom of the ramp?

Accepted Answer

$$3.8\ \mathrm{m/s}$$

Question 7

Which of the following equations correctly expresses Newton's Second Law for a system of forces?

Accepted Answer

$$F_{\mathrm{net}} = \sum_i F_i = m a$$

Question 8

A car of mass $$1,200\ \mathrm{kg} is $$moving at $$25\ \mathrm{m/s} on a $$level road. If the coefficient of kinetic friction between the tires and the road is $$0.80$$, what is the maximum possible frictional force that can act on the car?

Accepted Answer

$$9,408\ \mathrm{N}$$

Question 9

A $$0.5\ \mathrm{kg}$$ ball is dropped from rest from a height of $$10\ \mathrm{m}. $$Neglecting air resistance, what is its speed just before it hits the ground?

Accepted Answer

$$14\ \mathrm{m/s}$$

Question 10

A cyclist is coasting down a hill at constant speed. Which of the following statements is true about the forces acting on the cyclist?

Accepted Answer

The net force on the cyclist is zero because friction and drag balance the component of gravity down the hill.

Question 11

A $$2.0\ \mathrm{kg}$$ object is pulled across a horizontal surface with a force of $$10\ \mathrm{N} at an $$angle of $$30^\circ$$ above the horizontal. If the coefficient of kinetic friction is $$0.25$$, what is the acceleration of the object?

Accepted Answer

$$2.7\ \mathrm{m/s^2$}$$

Question 12

Which of the following best describes the drag force experienced by an object moving through air at high speed?

Accepted Answer

$$D = \frac{1}{2} C_D \rho A v^2$

Question 13

A $$5.0\ \mathrm{kg}$$ box is at rest on a horizontal surface. The coefficient of static friction is $$0.40. $$What is the minimum horizontal force required to start moving the box?

Accepted Answer

$$19.6\ \mathrm{N}$$

Question 14

A $$0.2\ \mathrm{kg}$$ puck slides on a frictionless surface at $$3.0\ \mathrm{m/s}. It $$then enters a rough patch where the coefficient of kinetic friction is $$0.10. $$How far does the puck travel before coming to rest?

Accepted Answer

$$4.6\ \mathrm{m}$$

Question 15

A $$1,000\ \mathrm{kg}$$ car is moving at $$20\ \mathrm{m/s}$$ when the driver slams on the brakes, causing the car to skid to a stop. If the coefficient of kinetic friction between the tires and the road is $$0.60$$, what is the stopping distance?

Accepted Answer

$$34\ \mathrm{m}$$

Question 16

A $$0.5\ \mathrm{kg}$$ object is thrown vertically upward with an initial speed of $$8.0\ \mathrm{m/s}. $$What is the maximum height it reaches?

Accepted Answer

$$3.3\ \mathrm{m}$$

Question 17

A $$10\ \mathrm{kg}$$ crate is pulled up a $$25^\circ$$ incline at constant speed. If the coefficient of kinetic friction is $$0.20$$, what is the magnitude of the pulling force parallel to the incline?

Accepted Answer

$$54\ \mathrm{N}$$

Question 18

Which of the following is the correct kinematic equation for displacement with constant acceleration?

Accepted Answer

$$x_f = x_i + v_i \Delta t + \frac{1}{2} a (\Delta t)^2$

Kinematics, Newton's Laws, and Applications: Study Notes for Physics 201 Exam #1

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