The physical quantity that does not have the dimensional formula [ML^-1T^-2] is

• force

• pressure

• stress

• modulus of elasticity

A dorce F is applied onto a square plate of side L. If the percentage error in determining L is 2 % and that in F is 4 %, the permissible percentage error in determining the pressure is

• 2 %

• 4 %

• 6 %

• 8 %

From a balloon moving upwards with a velocity of12 ms^-1, a packet is released when it is at a height of 65 m from the ground. The time taken by it to reach the ground is (take, g = 10 ms^-2)

• 5 s

• 8 s

• 4 s

• 7 s

A bus is moving with a velocity of 10 ms^-1 on a straight road. A scootorist wishes to overtake the bus in one minute. If the bus is at a distance of 1.2 km ahead, then the velocity with which he has to chase the bus is

• 20 ms^-1

• 25 ms^-1

• 30 ms^-1

• 40 ms^-1

5.

If the displacement of a body varies as the square of elapsed time, then its

• velocity is constant

• velocity varies non-uniformly

• acceleration is constant

• acceleration changes continuously

The magnitudes of a set of 3 vectors are given below. The set of vectors for which the resultant cannot be zero is

• 15, 20, 30

• 20, 20, 30

• 10, 20, 40

• 10, 10, 20

A ball dropped from a point A falls down vertically to C, through the mid-point B. The descending time from A to B and that from A to C are in the ratio

• 1 : 1

• 1 : 2

• 1 : 3

• $1 : \sqrt{2}$

A cricket ball is hit at an angle of 30° to the horizontal with a kinetic energy E. Its kinetic energy when it reaches the highest point is

• $\frac{\mathrm{E}}{2}$

• 0

• $\frac{2\mathrm{E}}{3}$

• $\frac{3\mathrm{E}}{4}$

If n bullets each of mass m are fired with a velocity v per second from a machine gun, the force required to hold the gun in position is

• (n + 1) mv

• $\frac{\mathrm{mv}}{{\mathrm{n}}^2}$

• mnv

• n²mv

The time required to stop a car of mass 800 kg, moving at a speed of 20ms^-1 over a distance of 25 m is

• 2 s

• 2.5 s

• 4 s

• 4.5 s