Question

1. State the difference between speed and velocity. Can a body move with uniform speed but with variable velocity? Explain with the help of an example. 

2. Show that a body thrown vertically upwards returns with the same magnitude of velocity

Answer 1

1. Speed is scalar quantity but velocity is a vector quantity. If a body moving along the circumstance of a circle with uniform speed, its velocity changes continuously with time.

2.

Consider a body projected upward from a point A with a velocity ‘u’. If the body reaches at B, the displacement becomes zero. Hence time taken to reach at B can be found.

S = ut + 1/2 at²

0 = ut + 1/2 × ^–10 t²

ut = 5t²

t = \(\frac{u}{5}\) ____(1)

The velocity at B can be found using the formula

V_B = u + at _____(2)

substitute eq(1) in eq(2)

V_B = u + ^-10\(\frac{u}{5}\)

= u – 2u

V_B = -u

∴ V_A = -V_B