Joey and McKaleb build an electromagnet by wrapping a wire around a nail and connecting the wire to both terminals of a battery. When they connect the battery, they discover that the electromagnet can pick up 5 paperclips. They want to be able to pick up 8 paperclips. Joey and McKaleb brainstorm and think of 4 ways to modify their experiment so the electromagnet will pick up 8 paperclips. Which of these do you think they should try?

A) All of these will increase the strength of the magnet since the strength of the magnet can be increased by changing the wire loops or the battery.

B) Number 1 and 2 will increase the magnetic force, but number 3 and 4 will not increase the strength of the magnet.

C) Number 1, 2 and 4 will increase the strength of the magnet, reversing the battery will make the magnet repel the paperclips.

D) None of these will work. The boys should add a real magnet in addition to the electromagnet if they want to pick up more paperclips.

How much force must a locomotive exert on a 12840-kg boxcar to make it accelerate forward at 0.490 m/s2?

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

The frequency of vibrations of a vibrating violin string is given by f = 1 2l t ρ where l is the length of the string, t is its tension, and ρ is its linear density.† (a) find the rate of change of the frequency with respect to the following. (i) the length (when t and ρ are constant) (ii) the tension (when l and ρ are constant) (iii) the linear density (when l and t are constant) (b) the pitch of a note (how high or low the note sounds) is determined by the frequency f. (the higher the frequency, the higher the pitch.) use the signs of the derivatives in part (a) to determine what happens to the pitch of a note for the following. (i) when the effective length of a string is decreased by placing a finger on the string so a shorter portion of the string vibrates df dl 0 and l is ⇒ f is ⇒ (ii) when the tension is increased by turning a tuning peg df dt 0 and t is ⇒ f is ⇒ (iii) when the linear density is increased by switching to another string df dρ 0 and ρ is ⇒ f is ⇒