Grade 11 : Physics - Motion (Straight/Plane) (Set 2) | Concept of Maths

Question 1

1. An athlete runs exactly halfway around a circular track of radius $R = 70$ m. What is the magnitude of their displacement?

A) $220$ m

B) $70$ m

C) $140$ m

D) $0$ m

Answer

Correct Answer: C

Displacement is the shortest distance between the start and end points. For a semi-circle, this is the diameter. $$Displacement = 2 \times R = 2 \times 70 = 140 \text{ m}$$

Question 2

2. A delivery drone travels $5$ km at a speed of $20$ km/h and then another $5$ km at a speed of $60$ km/h. What is the average speed for the entire $10$ km trip?

A) $40$ km/h

B) $30$ km/h

C) $45$ km/h

D) $25$ km/h

Answer

Correct Answer: B

Average speed = Total Distance / Total Time. $$t_1 = \frac{5}{20} = 0.25 \text{ h}, \quad t_2 = \frac{5}{60} = 0.0833 \text{ h}$$ $$V_{avg} = \frac{10}{0.25 + 0.0833} = \frac{10}{0.333} = 30 \text{ km/h}$$

Question 3

3. A car's speedometer reads $72$ km/h. What is this speed expressed in the SI unit (m/s)?

A) $20$ m/s

B) $25$ m/s

C) $15$ m/s

D) $10$ m/s

Answer

Correct Answer: A

To convert km/h to m/s, multiply by $\frac{5}{18}$. $$72 \times \frac{5}{18} = 4 \times 5 = 20 \text{ m/s}$$

Question 4

4. A mischievous monkey drops a mango from a tree branch $20$ m above the ground. How long does it take to reach the ground? (Take $g = 10 \text{ m/s}^2$)

Question 5

5. A robot moves $3$ meters North and then $4$ meters East. What is the magnitude of its total displacement from the starting point?

A) $7$ m

B) $5$ m

C) $1$ m

D) $12$ m

Answer

Correct Answer: B

Displacement is the vector sum. Since North and East are perpendicular: $$D = \sqrt{3^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5 \text{ m}$$

Question 6

6. If a train is moving at a constant velocity of $15$ m/s, what is its acceleration?

A) $0 \text{ m/s}^2$

B) $15 \text{ m/s}^2$

C) $9.8 \text{ m/s}^2$

D) $1 \text{ m/s}^2$

Answer

Correct Answer: A

Acceleration is defined as the rate of change of velocity. If velocity is constant, the change is zero, so acceleration is $0 \text{ m/s}^2$.

Question 7

7. On a Velocity-Time graph, a horizontal line (parallel to the time axis) represents:

A) Zero velocity

B) Constant acceleration

C) Constant velocity

D) The object is at rest

Answer

Correct Answer: C

A horizontal line on a v-t graph means the velocity value does not change as time passes, which implies constant (uniform) velocity.

Question 8

8. A biker applying brakes reduces their speed from $20$ m/s to $10$ m/s in $5$ seconds. What is the acceleration?

A) $2 \text{ m/s}^2$

B) $-2 \text{ m/s}^2$

C) $-5 \text{ m/s}^2$

D) $5 \text{ m/s}^2$

Answer

Correct Answer: B

$$a = \frac{v - u}{t} = \frac{10 - 20}{5} = \frac{-10}{5} = -2 \text{ m/s}^2$$ The negative sign indicates deceleration.

Question 9

9. Two cars $A$ and $B$ are driving on a highway in the same direction. Car $A$ is at $80$ km/h and Car $B$ is at $100$ km/h. What is the velocity of $B$ relative to $A$?

A) $180$ km/h

B) $-20$ km/h

C) $100$ km/h

D) $20$ km/h

Answer

Correct Answer: D

Relative velocity $V_{BA} = V_B - V_A$ (when moving in the same direction). $$V_{BA} = 100 - 80 = 20 \text{ km/h}$$

Question 10

10. Which of the following is a scalar quantity?

A) Distance

B) Displacement

C) Velocity

D) Acceleration

Answer

Correct Answer: A

Scalar quantities have only magnitude and no direction. Distance is a scalar, while displacement, velocity, and acceleration are vectors.

Question 11

11. A ball is thrown horizontally from the top of a building. What happens to its horizontal velocity component (ignoring air resistance)?

A) It increases due to gravity

B) It decreases until it hits the ground

C) It remains constant

D) It becomes zero immediately

Answer

Correct Answer: C

In projectile motion, there is no horizontal force (ignoring air), so the horizontal component of velocity ($u_x$) remains constant.

Question 12

12. A swimmer can swim at $4$ m/s in still water. They try to swim straight across a river flowing at $3$ m/s. What is their resultant speed?

A) $7$ m/s

B) $5$ m/s

C) $1$ m/s

D) $3.5$ m/s

Answer

Correct Answer: B

The swimmer's velocity and river velocity are perpendicular. $$V_{res} = \sqrt{4^2 + 3^2} = \sqrt{16 + 9} = 5 \text{ m/s}$$

Question 13

13. What does the area under a Velocity-Time graph represent?

A) Acceleration

B) Speed

C) Time

D) Displacement

Answer

Correct Answer: D

The integral of velocity with respect to time (area under v-t graph) gives the change in position, which is displacement.

Question 14

14. A particle moves in a circle of radius $r$ with constant speed $v$. The acceleration is:

A) Directed towards the center

B) Directed away from the center

C) Zero, because speed is constant

D) Tangential to the path

Answer

Correct Answer: A

In uniform circular motion, even if speed is constant, the direction of velocity changes. This creates centripetal acceleration directed toward the center.

Question 15

15. A stone is thrown vertically upwards with an initial velocity $u$. At the highest point, its velocity is:

A) $u$

B) $0$

C) $9.8 \text{ m/s}$

D) $-u$

Answer

Correct Answer: B

At the maximum height of a vertical throw, the object momentarily stops before falling back down, so its instantaneous velocity is $0$.

Question 16

16. A hiker walks $10$ km North, then turns and walks $10$ km South. What is their total distance traveled and total displacement?

A) Dist: $0$ km, Disp: $20$ km

B) Dist: $10$ km, Disp: $10$ km

C) Dist: $20$ km, Disp: $0$ km

D) Dist: $20$ km, Disp: $20$ km

Answer

Correct Answer: C

Distance is the total path length ($10 + 10 = 20$ km). Displacement is the change in position; since they returned to the start, displacement is $0$.

Question 17

17. The slope of a Position-Time ($x-t$) graph represents:

A) Velocity

B) Acceleration

C) Distance

D) Force

Answer

Correct Answer: A

Question 18

18. A car accelerates from rest at $4 \text{ m/s}^2$. How far does it travel in $3$ seconds?

A) $12$ m

B) $36$ m

C) $9$ m

D) $18$ m

Answer

Correct Answer: D

Using $s = ut + \frac{1}{2}at^2$: $$s = 0(3) + \frac{1}{2}(4)(3^2) = 2 \times 9 = 18 \text{ m}$$

Question 19

19. In projectile motion, the angle of projection for maximum horizontal range is:

A) $30^\circ$

B) $45^\circ$

C) $60^\circ$

D) $90^\circ$

Answer

Correct Answer: B

The range formula is $R = \frac{u^2 \sin(2\theta)}{g}$. Range is maximum when $\sin(2\theta) = 1$, which happens at $2\theta = 90^\circ$, or $\theta = 45^\circ$.

Question 20

20. A plane flies $400$ km East and $300$ km North. What is the magnitude of its displacement?

A) $700$ km

B) $100$ km

C) $500$ km

D) $350$ km

Answer

Correct Answer: C

$$D = \sqrt{400^2 + 300^2} = \sqrt{160000 + 90000} = \sqrt{250000} = 500 \text{ km}$$

Accepted Answer

Correct Answer: D

Using $h = ut + \frac{1}{2}gt^2$ with $u = 0$: $$20 = 0 + \frac{1}{2} (10) t^2 \implies 20 = 5t^2 \implies t^2 = 4 \implies t = 2 \text{ s}$$

Grade 11 : Physics - Motion (Straight/Plane) (Set 2) | Concept of Maths