Newton's Laws of Motion (Advanced)

CBSE Science. Optional Advanced level: pseudo forces in buses and lifts, g at a height and a depth, air resistance, torque = F d sin θ, balancing moments. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.

Open a printable sample sheet Cheat sheet: formulas and key points

Sample questions

Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.

Section A · multiple choice

1.
A lift accelerates upward at 3.5 m/s². For a 35 kg person inside it, the pseudo force seen from the lift's frame is:
1. 465.5 N, downward
2. 122.5 N, upward
3. 343 N, downward
4. 122.5 N, downward
Answer
(d) 122.5 N, downward
F = m × a(frame) = 35 × 3.5, opposite to the frame's acceleration
2.
Taking Earth's radius as 6,400 km and g = 9.8 m/s² at the surface, the value of g at a depth of 6,080 km is:
1. 0.49 m/s²
2. 9.31 m/s²
3. 19.11 m/s²
4. 0.02 m/s²
Answer
(a) 0.49 m/s²
g(1 − d/R) = 9.8 × (1 − 6,080/6,400)
3.
At a height 4R above the Earth's surface, the acceleration due to gravity becomes:
1. 1/5 of its surface value
2. 1/26 of its surface value
3. 1/125 of its surface value
4. 1/25 of its surface value
Answer
(d) 1/25 of its surface value
g_h/g = R²/(R + h)² = 1/(5)²

Section B · short answer

4.
A bus starts suddenly with an acceleration of 6 m/s². For a 30 kg passenger, find (a) the pseudo force seen from inside the bus and (b) its direction (forward or backward).
Answer
(a) 180 N; (b) backward
(a) 30 × 6; (b) opposite to the bus's acceleration
5.
An 85 kg student stands on a weighing scale in a lift that accelerates upward at 2.5 m/s². What does the scale read, in newtons? Take g = 9.8 m/s².
Answer
1,045.5 N
weight mg plus pseudo force ma, both downward: 85 × (9.8 + 2.5)

Section C · long answer

6.
A 35 kg person stands on a scale in a lift. Take g = 9.8 m/s². When the lift accelerates upward at 3.5 m/s², find (a) the pseudo force seen from inside the lift and (b) its direction (upward or downward), and (c) the scale reading. (d) What does the scale read when the lift accelerates downward at 3.5 m/s²?
Answer
(a) 122.5 N; (b) downward; (c) 465.5 N; (d) 220.5 N
(a) m × a = 35 × 3.5; (b) opposite to the lift's acceleration; (c) m(g + a); (d) m(g − a)

Fresh sheets for your child

In the app, every Newton's Laws of Motion (Advanced) sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.

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