A person riding on the roof of a freight train throws a ball forward. (a) If we ignore air drag and relative to the ground, is the ball moving faster or slower when the train is moving than when it is standing still? (b) Relative to the freight car, is the ball moving faster or slower when the train is moving than when the train is standing still?

The Sun puts out twice as much solar energy in 2 hours as it does in 1 hour. But the solar power of the Sun is the same from one hour to the next. Distinguish between the terms solar energy and solar power.

On a TV screen, red, green and blue spots of fluorescent materials are illuminated at a variety of relative intensities to produce a full spectrum of colors. What dots are activated to produce yellow? Magenta? White?

Multiple-Concept Example 10 reviews the approach and some of the concepts that are pertinent to this problem. The drawing shows a model for the motion of the human forearm in throwing a dart. Because of the force $\overrightarrow{\mathbf{M}}$ applied by the triceps muscle, the forearm can rotate about an axis at the elbow joint. Assume that the forearm has the dimensions shown in the drawing and a moment of inertia of $0.065 \mathrm{~kg} \cdot \mathrm{m}^2$ (including the effect of the dart) relative to the axis at the elbow. Assume also that the force $\overrightarrow{\mathbf{M}}$ acts perpendicular to the forearm. Ignoring the effect of gravity and any frictional forces, determine the magnitude of the force $\overrightarrow{\mathbf{M}}$ needed to give the dart a tangential speed of $5.0 \mathrm{~m} / \mathrm{s}$ in $0.10 \mathrm{~s}$, starting from rest.

A man holds a $178-\mathrm{N}$ ball in his hand, with the forearm horizontal (mentioned the drawing). He can support the ball in this position because of the flexor muscle force $\vec{M}$, which is applied perpendicular to the forearm. The forearm weighs $22.0 \mathrm{~N}$ and has a center of gravity as indicated. Find (a) the magnitude of $\overrightarrow{\mathbf{M}}$.

In the given figure, one end of a uniform beam of weight 222 N is hinged to a wall; the other end is supported by a wire that makes angles $\theta=30.0^{\circ}$ with both wall and beam. Find the vertical components of the force of the hinge on the beam.

The wheels, axle, and handles of a wheelbarrow weigh $60.0 \mathrm{~N}$. The load chamber and its contents weigh $525 \mathrm{~N}$. The drawing shows these two forces in two different wheelbarrow designs. To support the wheelbarrow in equilibrium, the man's hands apply a force $\overrightarrow{\mathbf{F}}$ to the handles that is directed vertically upward. Consider a rotational axis at the point where the tire contacts the ground, directed perpendicular to the plane of the paper. Find the magnitude of the man's force for both designs.

Two children hang by their hands from the same tree branch . The branch is straight, and grows out from the tree trunk at an angle of $27.0^{\circ}$ above the horizontal. One child, with a mass of 44.0 kg, is hanging 1.30 m along the branch from the tree trunk. The other child, with a mass of 35.0 kg, is hanging 2.10 m from the tree trunk . What is the magnitude of the net torque exerted on the branch by the children? Assume that the axis is located where the branch joins the tree trunk and is perpendicular to the plane formed by the branch and the trunk.

The formula that relates the speed, frequency, and wavelength of electromagnetic waves, $v=f \lambda$, was known before relativity was developed. Relativity has not changed this equation, but it has added a new feature to it. What is that feature?

What does Einstein's first postulate reveal about absolute motion?

A person riding on the roof of a freight train fires a gun pointed forward. Relative to the freight car, is the bullet moving faster or slower when the train is moving than when the train is standing still?

Which of the following muscles is NOT a rotator cuff muscle? Select one:

• A) supraspinatus
• B) levator scapulae
• C) subscapularis
• D) teres minor

A person riding on the roof of a freight train fires a gun pointed forward. Relative to the ground, is the bullet moving faster or slower when the train is moving than when it is standing still?

If stationary observers measure the shape of a passing object to be exactly circular, what is the shape of the object when viewed face-on by observers on board the object, traveling with it?