A body starts moving from rest on a horizontal ground such that the position vector of the body with respect to its starting point is given by \(r= 2 t\hat{i}+3t^2\hat j\). The equation of the trajectory of the body is:
1. \(y =1.5x\)
2. \(y =0.75x^2\)
3. \(y =1.5x^2\)
4. \(y =0.45x^2\)
| 1. | \(\vec{v}_{\text {avg }}=\frac{1}{2}\left[\vec{v}\left(t_1\right)+\vec{v}\left(t_2\right)\right]\) |
| 2. | \(\vec{v}(t)=\vec{v}(0)+\vec{a} t\) |
| 3. | \(\vec{r}({t})=\vec{r}(0)+\vec{v}(0){t}+\frac{1}{2} \vec{a}{t}^2\) |
| 4. | \(\vec{v}_{\text {avg }}=\frac{\left[\vec{r}\left(t_2\right)-\vec{r}\left(t_1\right)\right]}{\left(t_2-t_1\right)}\) |
A particle moves in space such that:
\(x=2t^3+3t+4;~y=t^2+4t-1;~z=2\sin\pi t\)
where \(x,~y,~z\) are measured in meters and \(t\) in seconds. The acceleration of the particle at \(t=3\) seconds will be:
| 1. | \(36 \hat{i}+2 \hat{j}+\hat{k} \) ms-2 |
| 2. | \(36 \hat{i}+2 \hat{j}+\pi \hat{k} \) ms-2 |
| 3. | \(36 \hat{i}+2 \hat{j} \) ms-2 |
| 4. | \(12 \hat{i}+2 \hat{j} \) ms-2 |
A particle starts moving with constant acceleration with initial velocity (\(\hat{\mathrm{i}}+5\hat{\mathrm{j}}\)) m/s. After \(4\) seconds, its velocity becomes (\(3\hat{\mathrm{i}}-2\hat{\mathrm{j}}\)) m/s. The magnitude of its displacement in 4 seconds is:
1. \(5\) m
2. \(10\) m
3. \(15\) m
4. \(20\) m
A river is flowing from east to west at a speed of \(5\) m/min. A man on south bank of river, capable of swimming \(10\) m/min in still water, wants to swim across the river in shortest time. He should swim:
| 1. | Due north |
| 2. | Due north-east |
| 3. | Due north-east with double the speed of the river |
| 4. | None of the above |
In the given figure, \(a=15\) m/s2 represents the total acceleration of a particle moving in the clockwise direction in a circle of radius \(R=2.5\) m at a given instant of time. The speed of the particle is:
1. \(4.5\) m/s
2. \(5.0\) m/s
3. \(5.7\) m/s
4. \(6.2\) m/s
Two bullets are fired horizontally and simultaneously towards each other from the rooftops of two buildings (building being \(100~\text{m}\) apart and being of the same height of \(200~\text{m}\)) with the same velocity of \(25~\text{m/s}.\) When and where will the two bullets collide?
\((g = 10~\text{m/s}^2)\)
| 1. | After \(2~\text{s}\) at a height of \(180~\text{m}\) |
| 2. | After \(2~\text{s}\) at a height of \(20~\text{m}\) |
| 3. | After \(4~\text{s}\) at a height of \(120~\text{m}\) |
| 4. | They will not collide. |
A car starts from rest and accelerates at \(5~\text{m/s}^{2}.\) At \(t=4~\text{s}\), a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at \(t=6~\text{s}?\)
(Take \(g=10~\text{m/s}^2\))
| 1. | \(20\sqrt{2}~\text{m/s}, 0~\text{m/s}^2\) | 2. | \(20\sqrt{2}~\text{m/s}, 10~\text{m/s}^2\) |
| 3. | \(20~\text{m/s}, 5~\text{m/s}^2\) | 4. | \(20~\text{m/s}, 0~\text{m/s}^2\) |
| 1. | \(24 :1\) | 2. | \(1:720\) |
| 3. | \(1:60\) | 4. | \(2:5\) |
| 1. | \(3000~\text{m}\) | 2. | \(2800~\text{m}\) |
| 3. | \(2000~\text{m}\) | 4. | \(1000~\text{m}\) |
A boy runs on a circular track of radius \(R\) (in km) with a speed of \(\dfrac{πR}{2}\) km/h in the clockwise direction for \(3\) h and then with \(πR\) km/h in the anticlockwise direction for \(1\) h. The magnitude of his displacement will be:
1. \(\dfrac{πR}{2}\)
2. \(\dfrac{R}{\sqrt{2}}\)
3. \(\dfrac{3πR}{2}\)
4. \(\sqrt{2}R\)
In a two-dimensional motion, the instantaneous speed of a particle remains constant at a positive value \(v_0.\) Which of the following statements must always be true?
| 1. | The particle has zero acceleration. |
| 2. | The particle’s acceleration is increasing. |
| 3. | The particle’s acceleration always lies in the plane of motion. |
| 4. | The particle necessarily moves in a uniform circular path. |
| Assertion (A): | The maximum height of a projectile is always \(25\)% of the maximum range. |
| Reason (R): | For maximum height, the projectile should be projected at \(90^\circ.\) |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True and (R) is False. |
| 4. | (A) is False and (R) is True. |
A particle moves with constant angular velocity in a circle. During the motion its:
| 1. | Energy is conserved |
| 2. | Momentum is conserved |
| 3. | Energy and momentum both are conserved |
| 4. | None of the above is conserved |
Six particles situated at the corners of a regular hexagon of side \(a\) move at constant speed \(v\). Each particle maintains a direction towards the particle at the next. The time which the particles will take to meet each other is:
1. \(\frac{2 a}{v}~\text{sec}\)
2. \(\frac{a}{v}~\text{sec}\)
3. \(\frac{2 a}{3v}~\text{sec}\)
4. \(\frac{3 a}{v}~\text{sec}\)