Physics Semester 2 Equation Answers

A stone with a mass of 1.0 kg is tied to the end of a light string which keeps it moving in a circle with a constant speed of 4.0 m/s on a perfectly smooth horizontal tabletop. The radius of the path is 0.60 m. How much work does the tension in the string do on the stone as it makes one-half of a complete circle?

0 J

You carry a 7.0 kg bag of groceries 1.2 m above the ground at a constant speed across a 2.7 m room. How much work do you do on the bag in the process?

0 J

Two air track carts move along an air track towards each other. Cart A has a mass of 450 g and moves towards the right with a speed of 0.850 m/s. Cart B has a mass of 300 g and moves towards the left with a speed of 1.12 m/s. What is the total momentum of this two cart system?

0.047 kg x m/s to the right

A 0.140 kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground and bounces. It rebounds with an upward velocity of 1.00 m/s. What is the change of the ball's momentum during the bounce?

0.308 kg x m/s upwards

It requires 0.30 kiloJoules of work to fully drive a stake into the ground. If the force needed to drive the stake in the ground is 828 N, how long is the stake?

0.36 m

What is the minimum energy needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

1.10 MJ

A 100 g ball falls from a window that is 12 meters above ground level and experiences no significant air resistance as it falls. What is its momentum when it strikes the ground?

1.5 kg x m/s

A certain battery charger uses 12 W of power. At 6.0 cents per kilowatt-hour, how much does it cost to charge batteries for a full day?

1.7 cents

A 0.140 kg baseball is thrown with a velocity of 27.1 m/s. It is struck by a bat with an average force of 5.00 x 10^3 N, which results in a velocity of 37.0 m/s in the opposite direction from the original velocity. How long were the bat and ball in contact?

1.79 x 10^-3 seconds

A 328 kg car is moving at 19.1 m/s in the positive x direction hits from behind a second car moving at 13.0 m/s in the same direction. If the second car has a mass of 790 kg and a speed of 15.1 m/s right after the collision, what is the velocity of the first car after this sudden collision?

14.0 m/s

A 60 kg skier pushes off the top of a friction-less hill with an initial speed of 4.0 m/s. How fast will she be moving after dropping 10 m in elevation?

15 m/s

A child pulls a wagon with a force of 75 N. If the wagon moves a total of 42 m in 3.1 min, what is the average power delivered by the child?

17 W

An ideal spring that has a spring constant of 2500 N/m is stretched 4.0 cm. How much work is required to stretch the spring by 4.0 cm?

2.0 J

How many joules of energy are used by a 1.0 hp motor that runs for 1 hour?

2.7 MJ

The figure shows a famous roller coaster ride (height of 50 m and 25 m). You can ignore friction. If the roller coaster leaves point Q from rest, what is its speed at the top of the 25 m peak?

22 m/s

When a car of mass 1167 kg accelerates from 10.0 m/s to some final speed, 4.00 x 10^5 J of work are done. Find the final speed.

28.0 m/s

What is the minimum energy needed to lift a 1.0 kg rocket to a height of 200 km to give it a speed of 8.0 km/s at that height?

34 MJ

A bead is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is friction-free, and there is no appreciable air resistance. What is the speed of the bead at point C?

34 m/s

A railcar of unknown mass is moving down a rail at 56.2 km/hr. It catches up and runs into a railcar that has a mass of 3.75 x 10^3 kg and is moving at 4.72 m/s. They hook together and proceed to move at 10.5 m/s. What is the unknown mass of the first railcar?

4.25 x 10^3 kg

A golf club exerts an average horizontal force of 1.0 x 10^3 N on a 0.045 kg golf ball that is initially at rest on the tee. The club is in contact with the ball for 1.8 ms. What is the speed of the golf ball just as it leaves the tee?

40. m/s

A prankster drops a water balloon from the top of a building. If the balloon is traveling at 29.1 m/s when it strikes a window ledge that is 1.5 m above the ground, how tall is the building? (neglect air resistance)

45 meters

A traveler pulls on a suitcase strap at an angle of 36 degrees above the horizontal ground. If 555 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap?

46 N

Astronaut Jennifer's lifeline to her spaceship comes loose and she finds herself stranded, floating 100.0 m away from the mothership. She suddenly throws her 2.000 kg wrench at 20.0 m/s in a direction away from the ship. If she and her spacesuit have a combined mass of 2000 kg, how long does it take her to coast back to her spaceship?

500.0 seconds

Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of 37.0 degrees above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?

575 J

A golf ball of mass 0.050 kg is at rest on the tee. Just after being struck, it has a velocity of 102 m/s. If the club and ball were in contact for 0.81 ms, what is the average force exerted on the ball by the club?

6.3 kN

A rock falls from a vertical cliff that is 4.0 meters tall and experiences no significant air resistance as it falls. At what speed will its gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy?

6.3 m/s

A 1200 kg ore cart is rolling at 10.8 m/s across a flat, friction-free surface. A crane suddenly drops 858 kg of ore vertically into the cart. How fast does the car move just after being loaded with the ore?

6.30 m/s

A 1200 kg car moving at 15.6 m/s suddenly collides with a stationary car of mass 1500 kg. If the two vehicles lock together, what is their combined velocity immediately after the collision?

6.9 m/s

At what minimum rate is a 60.0 kg boy using energy when, in 8.00 s, he runs up a flight of stairs that is 10.0 m in height?

735 W

If the work done to stretch an ideal spring by 4.0 cm is 6.0 J, what is the spring constant of this spring?

7500 N/m

A girl of mass 55 kg throws a ball of mass 0.80 kg against a wall. The ball strikes the wall horizontally with a speed of 25 m/s, and it bounces back with this same speed. The ball is in contact with the wall 0.050 seconds. What is the magnitude of the average force exerted on the wall by the ball?

8.0 x 10^2 N

A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0 m above the ground. What is the mass of the box?

8.9 kg

A 1500 kg car accelerates from rest to 25 m/s in 7.0 s. What is the average power delivered by the engine?

90 hp

How much work would a child do while pulling a 12 kg wagon a distance of 4.3 m with a 22 N force?

95 J

If the units of your answer are kg x m2/s3, which of the following types of quantities could your answer be?

Power

A stone can slide down one of four different frictionless ramps as shown in the figure. For which ramp will the speed of the stone be greatest at the botto,?

The speed will be the same for all ramps