Question

A person applies a constant horizontal force of 84 N to a block of ice on a smooth horizontal floor. Neglect friction. The block starts from rest and moves 11 m in 4.9 s.

(calculators permitted in this question)

(a) What is the mass of the block of ice?

m???ice =  kg

(b) If the person stops pushing at the end of 4.9 s, how far does the block move in the next 4.9 s?

d =  m

Answer 1

Answer 2

SOLUTION ;

Ice block moves 11.0 m in 4.9 sec. Initial speed is zero.

Hence, using formula :

s = ut + 1/2 a t^2 

=> 11.0 = 0 + 1/2 a (4.9)^2

=> 11.0 = 12.005 a 

=> a = 11.0 / 12.005 = 0.9163 m/sec^2 

a.

So,

Mass of the block, m 

= F/a 

= 84 / 0.9163 kg 

= 91.67 kg 

Mass of ice block is = 91.67 kg (ANSWER).

b.

Speed of block at t = 4.9 sec :

v4.9 = u + at = 0 + 0.9163 * 4.9 = 4.49 m/s

So distance moved in next 4.9 sec when force is no more applied : 

= v4.9  * (t) 

= 4.49 * 4.9

= 22 m 

Distance moved in next 4.9 sec = 22 m (ANSWER)