A tennis ball is lightly thrown vertically upwards to be struck by the racquet at the peak of the trajectory of the ball. A 350 g tennis racquet hits the ball with a velocity of 30. m⋅s−1. Both racquet and ball move with a horizontal velocity of 25 m⋅s−1 immediately after the collision. What is the mass of the ball, in grams?

In 1980, alfa romeo introduced the first system to smooth a rough idle caused by ignition and camshaft timing changes.

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 ⇒

What part of the ear is names after tools, such as the hammer and the anvil?