A 20 N force moving an object 5 m in its direction does 100 J of work, and a 4 kg object moving at 5 m/s has kinetic energy 50 J, so this IB sheet opens with a work value and a kinetic energy value. The answers record 50 W and 80 percent.
Key Takeaways
20 N over 5 m in the force's direction gives 100 J of work (Q1).
A 4 kg object at 5 m/s has 50 J of kinetic energy (Q2).
Q6 records 80 percent.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.The work done when a force of 20 N moves an object 5 m in the direction of the force is
(a) 4 J(b) 25 J(c) 100 J(d) 500 J
2.The kinetic energy of a 4 kg object moving at 5 m/s is
(a) 10 J(b) 20 J(c) 50 J(d) 100 J
3.A device transfers 200 J of energy in 4 s. Its power is
(a) 50 W(b) 200 W(c) 800 W(d) 0.02 W
4.The gravitational potential energy gained when a 2 kg mass is lifted through 3 m is approximately
(a) 6 J(b) 59 J(c) 196 J(d) 588 J
5.The unit of power is equivalent to
(a) J/s(b) N m(c) kg m/s(d) J
6.A machine receives 300 J of energy and wastes 60 J. Its efficiency is
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.State a situation in which the work done by a force is zero even though the object moves.
8.State the principle of conservation of energy.
9.Define the term power.
10.Describe the energy transformations that occur when a ball is thrown upward and returns to its starting point.
11.A car doubles its speed. State the factor by which its kinetic energy increases.
12.State the relationship between the work done by a net force and the change in kinetic energy of an object.
13.Define efficiency and state its unit.
14.Explain why lifting a heavy box quickly and slowly over the same height requires the same work but different power.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A car of mass 1000 kg accelerates from rest to 20 m/s. Using E_k = ½mv², calculate the kinetic energy gained.
16.A 5 kg mass is lifted vertically through 10 m. Using E_p = mgh with g = 9.8 m/s², calculate the gain in gravitational potential energy.
17.A motor transfers 1500 J of energy in 3 s. Using P = E ÷ t, calculate the power output.
18.A ball is dropped from a height of 5 m. Using energy conservation, mgh = ½mv², calculate its speed just before it hits the ground. Use g = 9.8 m/s².
19.A student of mass 60 kg climbs a flight of stairs of height 5 m in 4 s. Using P = mgh ÷ t with g = 9.8 m/s², calculate the power developed.
20.A friction force of 12 N acts on a block as it slides 8 m across a floor. Using W = Fs, calculate the work done by friction.
Answer Key
1. c) 100 J
2. c) 50 J
3. a) 50 W
4. b) 59 J
5. a) J/s
6. c) 80 percent
7. Refer to solution guide.
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20. Refer to solution guide.
End of Worksheet
People Also Ask
How much work does a 20 N force do moving an object 5 m in its direction?
100 J, option (c) in this worksheet (Q1).
What is the kinetic energy of a 4 kg object moving at 5 m/s?
50 J, option (c) in this worksheet (Q2).
What is the unit of power?
J/s, option (a) in this worksheet (Q5).
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