Question

A boy of 50kg hops with a horizontal velocity of 5m/s on stationary skateboard. The skateboard weights 4 kg . Find the velocity when the board starts rolling.​

Answer 1

Mass of the boy = 50 kg

Intial velocity of the boy = 5 m/s

Weight of the skateboard = 4 kg

Intial velocity of skateboard (the skateboard is stationery) = 0 m/s

According to Law of conservation of momentum:

$\boxed{\sf{m_a u_a +m_b u_b = m_a v_a + m_b v_b}}$

$\longrightarrow (50 × 5) + (4 × 0) = v(50 + 4)$

$\longrightarrow 250 + 0 = 54v$

$\longrightarrow 250 = 54v$

$\longrightarrow v = 250/54$

$\longrightarrow v = 4.62 m/s$

Therefore, the skateboard starts rolling at the speed of 4.62 m/s.

Answer 2

Answer:

i. The co-ordinates of B is (−5, 2).

ii. The co-ordinates of C is (5, −5).

iii. The point identified by the coordinates (−3, −5) is E.

iv. The point identified by the coordinates (2, −4) is G.

v. Abscissa means x co-ordinate of point D. So, abscissa of the point D is 6.

vi. Ordinate means y coordinate of point H. So, ordinate of point H is -3.

vii. The co-ordinates of the point L is (0, 5).

viii. The co-ordinates of the point M is (−