Finding work, energy, power, impulse and momentum of particles.
1. A worker pushes a wheelbarrow with the force of 40N over a level distance of 6m. If a frictional force of 24N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow?
a. 240 J
b. 216 J
c. 144 J
d. 96 J
e. 75 J
2. A satellite is held in orbit by a 2N gravitational force. Each time the satellite completes an orbit of circumference 80 000 km, the work done on it by gravity is:
a. 1.6 108 J.
b. 1.6 1011 J.
c. 6.4 1011 J.
d. 0.
e. None of the above.
3. Which of the following is an ex of a non conservative force?
a. gravity
b. magnetism
c. friction
d. Both choices A and B are valid.
e. Both choices A and C are valid.
4. A horizontal force of 200N is applied to a 55 kg cart across a 10 m level surface. If the cart accelerates at 2.0 m/s2, then what is the work completed by the force of friction as it acts to retard the motion of the cart?
a. -1 100 J
b. -900 J
c. -800 J
d. -700 J
e. -600 J
5. An amount of work equal to 1.50 J is necessary to compress the spring in a spring-gun. What is the "launch speed" of a 15 g marble?
a. 14 m/s
b. 15 m/s
c. 18 m/s
d. 21 m/s
e. 23 m/s
6. A 20 N crate starting at rest slides down a rough 5 m long ramp, inclined at 25 with the horizontal. 20 J of energy is lost to friction. What would be the speed of the crate at the bottom of the incline?
a. 0.98 m/s
b. 1.9 m/s
c. 3.2 m/s
d. 4.7 m/s
e. 5.6 m/s
7. A 0.12 kg ball is moving at 6m/s while it is hit by a bat, causing it to reverse direction and have a speed of 14m/s. What is the change in the magnitude of the momentum of the ball?
a. 0.39 kgm/s
b. 0.42 kgm/s
c. 1.3 kgm/s
d. 2.4 kgm/s
e. 3.2 kgm/s
8. Lonnie pitches a baseball of mass 0.20kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Lonnie with a return speed of 60m/s. If the bat is in contact with the ball for 0.05 s, what is the impulse experienced by ball?
a. 360 Ns
b. 20 Ns
c. 400 Ns
d. 9.0 Ns
e. 35 Ns
9. A grindstone spinning at the rate of 8.3 rev/s has what approximate angular speed?
a. 3.2 rad/s
b. 26 rad/s
c. 52 rad/s
d. 81 rad/s
e. 97 rad/s
10. A 0.30 m-radius automobile tire rotates how many rad after starting from rest and accelerating at a constant 2.0 rad/s2 over a 5.0-s interval?
a. 12.5 rad
b. 25 rad
c. 2.0 rad
d. 0.50 rad
e. 0.25 rad