 Lv 1122 points

• • ### After falling from rest from a height of 28 m, a 0.35-kg ball rebounds upward, reaching a height of 18 m. ?

After falling from rest from a height of 28 m, a 0.35-kg ball rebounds upward, reaching a height of 18 m. If the contact between ball and ground lasted 2.2 ms, what average force was exerted on the ball? (Enter the magnitude.)

• ### A 1,360 -N crate ?

• • ### After falling from rest from a height of 28 m, a 0.35-kg ball rebounds upward, reaching a height of 18 m. ?

After falling from rest from a height of 28 m, a 0.35-kg ball rebounds upward, reaching a height of 18 m. If the contact between ball and ground lasted 2.2 ms, what average force was exerted on the ball? (Enter the magnitude.)

• ### Two boxes of fruit on a frictionless horizontal surface are connected by a light string as in the figure below?

Two boxes of fruit on a frictionless horizontal surface are connected by a light string as in the figure below, where m1 = 14 kg and m2 = 24 kg. A force of F = 68 N is applied to the 24-kg box.

(a) Determine the acceleration of each box and the tension in the string.

acceleration of m1     m/s2

acceleration of m2     m/s2

tension in the string     N

(b) Repeat the problem for the case where the coefficient of kinetic friction between each box and the surface is 0.10.

acceleration of m1     m/s2

acceleration of m2     m/s2

tension in the string     N

• ### A bomber is flying horizontally over level terrain at a speed of 290 m/s relative to the ground and at an altitude of 3.40 km.?

A bomber is flying horizontally over level terrain at a speed of 290 m/s relative to the ground and at an altitude of 3.40 km.

(a) The bombardier releases one bomb. How far does the bomb travel horizontally between its release and its impact on the ground? Ignore the effects of air resistance.

(c) The plane has a telescopic bombsight set so that the bomb hits the target seen in the sight at the moment of release. At what angle from the vertical was the bombsight set?

° forward from the vertical

• ### A projectile is launched with an initial speed of 48.0 m/s at an angle of 33.0° above the horizontal. ?

A projectile is launched with an initial speed of 48.0 m/s at an angle of 33.0° above the horizontal. The projectile lands on a hillside 3.60 s later. Neglect air friction. (Assume that the +x-axis is to the right and the +y-axis is up along the page.)

(a) What is the projectile's velocity at the highest point of its trajectory?

magnitude      m/s

direction      ° counterclockwise from the +x-axis

(b) What is the straight-line distance from where the projectile was launched to where it hits its target?

• ### A ball is thrown straight upward and returns to the thrower's hand after 2.60 s in the air. ?

A ball is thrown straight upward and returns to the thrower's hand after 2.60 s in the air. A second ball thrown at an angle of 28.0° with the horizontal reaches the same maximum height as the first ball.

• ### A home run is hit in such a way that the baseball just clears a wall 18 m high, located 112 m from home plate. ?

A home run is hit in such a way that the baseball just clears a wall 18 m high, located 112 m from home plate. The ball is hit at an angle of 33° to the horizontal, and air resistance is negligible. (Assume that the ball is hit at a height of 1.0 m above the ground.)

a) Find the initial speed of the ball.

m/s

(b) Find the time it takes the ball to reach the wall.

s

(c) Find the velocity components of the ball when it reaches the wall.

x-component  m/s

y-component m/s

Find the speed of the ball when it reaches the wall.

m/s

• ### A playground is on the flat roof of a city school, hb = 5.40 m above the street below (see figure).?

A playground is on the flat roof of a city school, hb = 5.40 m above the street below (see figure). The vertical wall of the building is h = 6.90 m high, to form a 1.5-m-high railing around the playground. A ball has fallen to the street below, and a passerby returns it by launching it at an angle of θ = 53.0° above the horizontal at a point d = 24.0 m from the base of the building wall. The ball takes 2.20 s to reach a point vertically above the wall.

(a) Find the speed at which the ball was launched.

m/s

(b) Find the vertical distance by which the ball clears the wall.

m

(c) Find the horizontal distance from the wall to the point on the roof where the ball lands.

m

• ### An artillery shell is fired with an initial velocity of 300 m/s at 52.0° above the horizontal. ?

An artillery shell is fired with an initial velocity of 300 m/s at 52.0° above the horizontal. To clear an avalanche, it explodes on a mountainside 41.5 s after firing. What are the x- and y-coordinates of the shell where it explodes, relative to its firing point?

x =

y =

• ### A fireman d = 54.0 m away from a burning building directs a stream of water from a ground-level fire hose at an angle of θi ?

A fireman d = 54.0 m away from a burning building directs a stream of water from a ground-level fire hose at an angle of θi = 31.0° above the horizontal as shown in the figure. If the speed of the stream as it leaves the hose is vi = 40.0 m/s, at what height will the stream of water strike the building?

• ### A person travels by car from one city to another with different constant speeds between pairs of cities. ?

A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 50.0 min at 85.0 km/h, 8.0 min at 80.0 km/h, and 45.0 min at 30.0 km/h and spends 60.0 min eating lunch and buying gas.

(a) Determine the average speed for the trip.

km/h

(b) Determine the distance between the initial and final cities along the route.

km

• ### A ball is thrown directly downward with an initial speed of 7.90 m/s, from a height of 29.2 m. ?

A ball is thrown directly downward with an initial speed of 7.90 m/s, from a height of 29.2 m. After what time interval does it strike the ground?

• ### A student throws a set of keys vertically upward to his fraternity brother, who is in a window 3.65 m above. ?

A student throws a set of keys vertically upward to his fraternity brother, who is in a window 3.65 m above. The brother's outstretched hand catches the keys 1.45 s later. (Take upward as the positive direction. Indicate the direction with the sign of your answer.)

(a) With what initial velocity were the keys thrown?

m/s

(b) What was the velocity of the keys just before they were caught?

• ### A student throws a set of keys vertically upward to his fraternity brother, who is in a window 3.65 m above. ?

A student throws a set of keys vertically upward to his fraternity brother, who is in a window 3.65 m above. The brother's outstretched hand catches the keys 1.45 s later. (Take upward as the positive direction. Indicate the direction with the sign of your answer.)

• ### The driver of a truck slams on the brakes when he sees a tree blocking the road. ?

The driver of a truck slams on the brakes when he sees a tree blocking the road. The truck slows down uniformly with acceleration

−5.55 m/s2

for 4.20 s, making skid marks 57.8 m long that end at the tree. With what speed does the truck then strike the tree?

• ### The diameter of a sphere is measured to be 4.40 in.?

The diameter of a sphere is measured to be 4.40 in.?

(a) Find the radius of the sphere in centimeters.

(b) Find the surface area of the sphere in square centimeters.

cm2

(c) Find the volume of the sphere in cubic centimeters.

cm3

• ### The radius of a circle is measured to be  (13.2 ± 0.7) m.  ?

The radius of a circle is measured to be

(13.2 ± 0.7) m.

Calculate each of the following and give the uncertainty in each value.

(a) the area of the circle

_____ m2 ± ______