1.
A 75 kg man climbs a staircase with a height of 4 m. What is the work done against gravity?
A
300 J
B
750 J
C
3000 J
D
4000 J
View Answer
Correct Answer: C — 3000 J
Explanation:
Work done = mgh = 75 × 10 × 4 = 3000 J.
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A 75 kg man climbs a staircase with a height of 4 m. What is the work done against gravity?
300 J
750 J
3000 J
4000 J
Correct Answer: C — 3000 J
Explanation:
Work done = mgh = 75 × 10 × 4 = 3000 J.
When a ball is thrown upward, its kinetic energy is converted into?
Electrical energy
Potential energy
Heat energy
Chemical energy
Correct Answer: B — Potential energy
Explanation:
As the ball rises, kinetic energy changes into potential energy.
The total energy of a body is the sum of which two forms of energy?
Work and energy
Heat and work
Kinetic and potential energy
Chemical and electrical energy
Correct Answer: C — Kinetic and potential energy
Explanation:
Mechanical energy is the sum of kinetic and potential energy.
What is the condition for work to be done by a force?
The force must be zero
There must be a displacement in the direction of the applied force
The object must be at rest
The displacement must be perpendicular to the force
Correct Answer: B — There must be a displacement in the direction of the applied force
Explanation:
Work is done when a force causes displacement in its direction.
If the displacement is zero, what is the work done by the force?
Infinite
Negative
Zero
Positive
Correct Answer: C — Zero
Explanation:
Work done is zero when there is no displacement.
A car of mass 1000 kg is moving at a speed of 20 m/s. What is its kinetic energy?
200 kJ
400 kJ
100 kJ
300 kJ
Correct Answer: A — 200 kJ
Explanation:
Kinetic energy = 1/2 mv² = 1/2 × 1000 × 20² = 200000 J = 200 kJ.