Physics Test

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Physics Test - 2

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Question 1
4 / -1

A particle has an initial velocity of 9 m/s due east and a constant acceleration of 2 m/s2 due west. The distance covered by the particle in the fifth second of its motion is

A
0 m

B
0.5 m

C
2 m

D
None of these

Solution

Explanation:

The displacement is indeed 0 but not the distance. the distance covered is 0.5 m.

Actually, the car is changing the direction of motion at 4.5 seconds. As such displacement between 4 and 5 seconds is 0 but still the car covers some distance.

The distance is the mod of displacement made by the car between 4 and 4.5 seconds + mod of the displacement between 4.5 and 5 seconds.

Displacement b/w 4 to 4.5 seconds = (9)(0.5) - (4.5² - 4²) = 4.5 - 4.25 = 0.25

Displacement b/w 4.5 to 4 seconds = (9)(0.5) - (5² - 4.5²) = 4.5 - 4.75 = -0.25

Displacement = 0, Distance = 0.5 m
Question 2
4 / -1

A body is projected at time t = 0 from a certain point on a planet’s surface with a certain velocity at a certain angle with the planet’s surface (assumed horizontal). The horizontal and vertical displacements x and y (in metres), respectively vary with time t (in seconds) as x = 10 √3 t and y = 10 t – t².

What is the value of acceleration due to the gravity on the planet’s surface?

A
1.0 ms^–2

B
2 ms^–2

C
4 ms^–2

D
9.8 ms^–2

Solution

Explanation:
Question 3
4 / -1

A ball, which is at rest, is dropped from a height of 'h' metres. As it bounces off the floor, its speed is 80% of what it was just before touching the ground. The ball will rise to a height of

A
0.94 h

B
0.80 h

C
0.75 h

D
0.64 h

Solution

Explanation:
Question 4
4 / -1

A stone is dropped from a certain height. After falling for 5 sec, the stone breaks through a pane of glass and instantaneously, loses half of its velocity. If the stone takes one more second to reach the ground, what is the height of the glass above the ground? (Given g = 10 m/s2)

A
60 m

B
50 m

C
30 m

D
20 m

Solution

Explanation:
Question 5
4 / -1

The Young's modulus of the material of a wire is 2 x 10¹⁰ Nm^–2. If the elongation strain is 1%, then the energy stored in the wire per unit volume (in Jm^–3) is

A
10⁶

B
10⁸

C
2 x 10⁶

D
2 x 10⁸

Solution

Explanation:

The energy stored in the wire per unit volume is given by:
Question 6
4 / -1

If Earth suddenly contracts to 1.5% of its present size, without any change in its mass, then how would the value of acceleration due to gravity change?

A
2%

B
3%

C
4%

D
5%

Solution

Explanation:
Question 7
4 / -1

A stone weighing 0.5 Kg tied to a rope of length 0.5 m revolves along a circular path in a vertical plane. The tension of the rope at the bottom point of the circle is 45 N. To what height will the stone rise if the rope breaks the moment the velocity is directed upwards? (g = 10m/s²)

A
2 m

B
4 m

C
6 m

D
8 m

Solution

Explanation:
Question 8
4 / -1

Two balls marked 1 and 2 of the same mass m and a third ball marked 3 of mass M are arranged over a smooth horizontal surface as shown in the figure. Ball 1 moves with a velocity v1toward balls 2 and 3. All collisions are assumed to be elastic. If M < m, the number of collisions between the balls will be

A
one

B
two

C
three

D
four

Solution

Explanation:

The first collision will be between balls 1 and 2. since both have the same mass, after the collision ball 1
win come to rest and ball 2 win move with speed v₁. This ball will collide with the stationary ball 3 .
Alter this second collision, let v₂ and v₃ be the speeds of balls 2 and 3 respectively. since the collisions
are elastic, v₂ and v₃are given by.

(i)

If M<m, it follows from (i) and (ii) that v₂<v₃ and both have the same direction. Therefore, ball 2
cannot collide with ball 3 again. Hence there are only two collisions.
Question 9
4 / -1

A 1 kg ball moving at 12 m/s collides head-on with a 2 kg ball moving in the opposite direction at 24 m/s. What is the velocity of each ball after the impact, if the coefficient of restitution is 2/3 ?

A
v₁ = -28 m/s, v₂ = -4 m/s

B
v₁ = 20 m/s, v₂= 2 m/s

C
v₁ = -30 m/s, v₂= -18 m/s

D
v₁ = -20 m/s, v₂= -4 m/s

Solution

Explanation:

Using conservation of linear momentum
Question 10
4 / -1

Three particles, each of mass 'm' g, are situated at the vertices of an equilateral triangle ABC of side l cm (as shown in the figure). The moment of inertia of the system about a line AX perpendicular to AB in the plane of ABC in gram-cm² unit will be

A
(3/4) ml²

B
2 ml²

C
(5/4) ml²

D
(3/2) ml²

Solution

Explanation:

The moment of inertia of