HONORS PHYSICS – Work & Energy REVIEW
1) A wind blowing at 25.0° exerts a force of 675 N on the sail of a boat which in turn is propelled 1.55
km, 45.0°. (Consider directions as viewed from overhead.) Find the work done by the wind.
2) A body of mass 1kg is thrown upwards with a velocity 20m/s. It momentarily comes to rest after
attaining a height of 18 m. How much energy is lost due to air friction?
3) A skier weighing 700N goes over a frictionless circular hill as shown. If the skier's
speed at point A is 9.2m/s, what is his speed at the top of the hill (point B)? Angle
between A and B is 45o .
4) A spring (k = 200 N/m) is suspended with its upper end supported from a ceiling.
With the spring hanging in its equilibrium configuration, an object (mass = 2.0 kg) is attached to the
lower end and released from rest. What is the speed of the object after it has fallen
4.0 cm?
5) The graph shows the force component along the displacement as a function of the
magnitude of the displacement. Determine the work done by the force during the
interval from 2 to 10 m.
6) A certain car’s drive-train produces a force of 5300 N as it accelerates from 0 to 60
mph in 10.0 seconds. If this acceleration covers a distance of 125 m, determine the
power output of the car’s engine.
7) A 2500 kg car is running on flat ground at 35 m/s. Just as it reaches the bottom of a hill with slope 25°
the engine cuts out. How far up the hill will the car move, measured along the road? Neglect friction.
8) An electric light bulb is rated at 150 W. (a) How much electric energy is transferred in 55 minutes?
(b) In how much time would this bulb use as much electric energy as there is chemical energy in a 150
Calorie cookie (628,500 J)?
9) A weight lifter raises a 150 kg barbell from the floor to a height of 2.2 m in 0.80 sec. What is his
power output assuming constant speed?
10) A 4.00 kg box is pushed 2.00 m across a level surface by an applied force of 32.0 N, 0°. The box then
slides an additional 3.00 m before coming to a rest. (a) Determine the amount of friction. (b) Determine
the box’s maximum speed over the 5.00 m distance traveled.
11) A skateboarder with mass 76.5 kg skates back and forth in a "half pipe" (a semicircle) with radius
8.00 m. In order to get vertical (i.e. reach the lip of the half pipe),
a) what speed must the skater have at the lowest point in the pipe?
b) What is the total energy of the skater?
When the skater reaches a point 2.00 m higher than the lowest point find:
c) the skater's potential energy ( Use the lowest point as a reference for PE )
d) the skater's kinetic energy
e) the skater's speed.
12) A 100 kg piano is pushed at a constant speed up a 4.00 m ramp inclined at an angle of 10.0o . It takes
220 N to push the piano and there is 50.0 N of friction.
a) Find the work done by the person pushing.
b) Find the work done by friction.
c) Find the work done by gravity.
d) Find the work done by the normal force.
13) An archer puts a 0.30 kg arrow to the bowstring. An average force of 201 N is exerted to draw the
string back 1.3 m.
a) Assuming no frictional loss, with what speed does the arrow leave the bow?
b) If the arrow is shot straight up, how high does it rise?
14) See diagram at right. The horizontal surface on which the block slides is
frictionless. The speed of the block before it touches the spring is 6.0m/s. How fast is
the block moving at the instant the spring has been compressed 15cm? k = 2000N/m.
15) A spring with constant k = 2500 N/m is mounted vertically and then compressed 10.0 cm. A 250
gram ball is placed on top of the spring and then the ball and spring are released.
(a) How high above its starting position will the ball be propelled?
(b) What is the ball’s maximum speed during its upward flight?
16) A skydiver with mass 85.0 kg drops out of a hovering helicopter and falls 700.0 m before pulling the
ripcord and releasing his parachute. (a) Find the work done by gravity. (b) What would be the speed just
before opening the chute if there was no air resistance? (c) If the actual speed just before the chute opens
is 50.0 m/s, what was the average force of air resistance? (d) Once the parachute is open, the air does
work in amount −175 kJ as the speed is decreased to 6.00 m/s. What distance does the skydiver fall while
this happens?
17) A 2.2kg block is moving with a speed of 5.0m/s at the top of a ramp that is inclined at 25o.
The coefficient of friction on the ramp is 0.45. The length of the ramp
is 3.4m. The block reaches the bottom and makes a smooth transition
to the floor (frictionless). How far is the spring compressed if the
spring constant is 250N/m?
18) Two boxes are connected to each other as shown. The system is released
from rest and the 1.00-kg box falls through a distance of 1.00 m. The surface of
the table is frictionless. What is the kinetic energy of box B just before it
reaches the floor?
REVIEW ANSWERS:
1) 983 kJ
2) 23.6J
3) 5.21m/s
4) 0.79 m/s
5) 180 J
6) 66 kW
7) 148 m
15) a. 5.00 m, b. 9.90 m/s
8) a. 495 kJ, b. 1.2 hrs
16) a. 583 kJ, b. 117 m/s, c. 681 N, up, d. 84.4 m
9) 4.0 kW
17) 0.478m
10) a. 12.8 N, b. 4.38 m/s
11) a. 12.5 m/s, b. 6000 J, c. 1500 J, d. 4500 J, e. 10.8 m/s
12) a. 880 J, b. –200 J, c. –681 J, d. 0 J
13) a. 42 m/s, b. 89 m
18) 2.45J
14) 3.7 m/s
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