1. a) there is no force acting on it. and also,
c) the combination of forces acting on it balance each other..
both a and c must be true.
2. d) a force is not required to keep it moving with a uniform velocity.
a force is needed for all other options.
3. the deceleration caused by friction = a .
a = (v-u)/t = 0-4 / 2 = -2 m/sec/sec
frictional force = - 2 kg * 2 m/sec/sec = - 4 Newtons
so a force of +4N is needed to cancel friction. Then the body will continue at the uniform velocity of 4 m/sec
The blocks of 1 kg, 2kg, and 3 kg are all in equilibrium - stationary - when there are acted up on by two or more forces on each block. let g be acceleration due to gravity.
T1 and weight of block 3 kg are balancing. Hence T1 = 3 * g newtons.
T1, T2 and weight of 2 kg block are acting on mass of 2 kg. they are balanced. T1 and weight are acting down wards. T2 is upwards.
T1 + 2 * g = T2 => T2 = 3 g + 2 g = 5 g newtons
T3, T2 and weight of 1 kg block are acting on mass of 1kg.
T3 = T2 + 1 * g = 6 * g newtons.